生平

永嘉二年（308年）张轨患病不能说话，时兄长张寔仍在朝中，故张茂就代父管理凉州事务。建兴元年（312年），南阳王司马保曾经请张茂作自己的从事中郎，后又推荐他任散骑侍郎、中垒将军，但张茂都不应命。次年，张茂被徵召为侍中，但张茂以父亲年老为由推辞。不久，改拜平西将军、秦州刺史。

建兴八年（320年），张寔被部下所杀，因其子骏年幼，张茂就代摄其位，杀刘弘数百名同党。时凉州府推举张茂为大都督、太尉、凉州牧，但张茂不肯受，只以使持节平西将军、凉州牧职位，又以张寔子张骏为抚军将军、武威太守、西平公。。

建兴十年（322年），张茂派韩璞率兵占领陇西南安郡境，并在当地置秦州。建兴十一年（323年），前赵刘曜派部将刘咸攻冀城，呼延晏攻桑壁，时临洮人翟楷及石琮等又驱逐其地方官员响应刘曜，刘曜本人更发兵二十八万五千人沿黄河列阵百多里，张茂设在黄河沿岸守戍的军队望风奔逃，刘曜更声言面率大军渡河，直攻姑臧，遂震动河西。张茂听从参军马岌所言出屯姑臧城东的石头，在听参军陈珍分析刘曜其实不会尽力攻凉后，便派陈珍出兵救援在冀城的韩璞。刘曜亦自知其强大的兵力有三分之二是因为人们怯于其声威而来，主力军队已经相当疲累，难以渡河进攻，于是一直按兵不动，想用声威胁服张茂。张茂最终派使者向前赵称藩，进献大量物品，刘则授张茂使持节、假黄钺、侍中、都督凉南北秦梁益巴汉陇右西域杂夷匈奴诸军事、太师、领大司马、凉州牧、领西域大都护、护氐羌校尉。封凉王。

建兴十二年（324年）张茂病死，享年四十八岁。前凉私下为张茂上諡号成公，刘曜则遣使赠太宰，諡成烈王。后来张祚称帝，追尊张茂为成王，庙号太宗。张茂临终时交代张骏「谨守人臣之节，无或失坠」。因张茂无子，张骏就被推举继位。

性格特徵

张茂为人谦虚恭敬，且又好学，不因为利禄而动心，又有志向及节操，有决定大事的能力。当时有一个人叫贾摹，不但出身凉州大姓，他也是张寔妻子的弟弟，势力很大。曾经有一首童谣这样说：「手莫头，图凉州。」张茂以此诱杀贾摹，终令凉州豪门大族不敢横行，更有助前凉张氏对凉州的管治。

注释

Early career

Zhang Mao first appeared in history in 308 when his father, Zhang Gui (张轨), the first Zhang Duke of Xiping and governor of Liang Province (凉州, modern central and western Gansu), suffered a stroke and was unable to speak, and therefore had Zhang Mao act as governor during his illness. When the unrelated Zhang Yue (张越) and Cao Que (曹怯) tried to take advantage of Zhang Gui's illness to have him replaced, the Zhangs resisted and convinced the powerful Sima Mo (司马模) the Prince of Nanyang that Zhang Gui should remain governor. At this time, Zhang Gui's oldest son and Zhang Mao's older brother Zhang Shi (张寔), who had previously been at Chang'an, returned to Liang Province and defeated and killed Cao, reaffirming the Zhangs' rule over the province.

During the subsequent governorship of Zhang Shi, Zhang Mao was one of his trusted generals. In 320, the magician Liu Hong (刘弘), who had spread rumors that the gods wished for him to be the ruler of Liang Province, convinced two of Zhang Shi's guards Yan She (阎涉) and Zhao Ang (赵卬) to assassinate Zhang Shi. Zhang Mao had Liu Hong arrested and executed by drawing and quartering. Because Zhang Shi's son Zhang Jun was still young (13 at the time), Zhang Shi's subordinates requested that Zhang Mao take over as governor and the Duke of Xiping, and he did so. He also issued a general pardon for the people in his domain – and this act is the main reason why his rule is commonly considered to mark the independence of Former Liang.

As ruler

Zhang Mao initially continued to claim to be a Jin vassal, as a governor and a duke. He appointed Zhang Jun, his nephew, as his heir. (Historical accounts are not clear whether Zhang Mao had sons of his own.) In 321, he started the construction of an impressive tower known as Lingjun Tower (灵钧台), but after Yan Zeng (阎曾) persuaded him that it was too costly and that Zhang Gui would have disapproved, he stopped the construction.

In 322, Zhang Mao had his general Han Pu (韩璞) seize the Longxi (陇西) and Nan'an (南安, together roughly modern Dingxi, Gansu) Commanderies – which appeared to be then under nominal Han Zhao control, while Han Zhao forces were battling the rebel Chen An, extending his domain east of the Yellow River.

However, in 323, after the Han Zhao emperor Liu Yao defeated Chen An, he continued on and reached the Yellow River, claiming to be ready to cross it. Zhang went into a battle posture, but negotiated peace, agreeing to submit to Han Zhao authority and offering tributes of horses, livestock, and jewels. Liu Yao created him the Prince of Liang and granted him the nine bestowments. Subsequently, Zhang Mao resumed the construction on Lingjun Tower, stating that its construction was necessary for defensive purposes, and strengthened the defenses of the capital Guzang (姑臧, in modern Wuwei, Gansu).

In summer 324, Zhang Mao grew ill. He told his nephew Zhang Jun to remain faithful to Jin, and also ordered that he not be buried as a prince, since his princely title was not granted by the Jin emperor. He died soon thereafter.

Era name

Most historical sources indicate that Zhang Mao, like his brother Zhang Shi, continued to use Emperor Min of Jin's era name Jianxing (both to show continued allegiance to Jin and to distance himself from Emperor Yuan of Jin and his line) but some sources indicate that he changed era name to Yongguang (永光 yǒng guāng 320–323). A current theory is that his era name was used internally while the Jianxing era name was used when communicating with other states.