He was described as "intelligent and quick-witted, had some knowledge of clerical work, was skilled in pellet shooting and archery, and was exceptionally agile.
He was born in 552 in Luoyang during Northern Zhou dynasty to Zhangsun Si (长孙兕) and a lady from Chigan (or Xue) clan.
During the marriage negotiations, both Northern Zhou and Ishbara Khagan showcased their native talents and selected brave warriors as envoys.
As a result, Zhangsun Sheng was dispatched as an envoy, serving as an assistant to Yuwen Shenqing to escort Princess Qianjin.
Taking advantage of his hunting trips, Sheng observed the geographical and military strengths and weaknesses of the Turks.
Upon returning, Sheng reported the detailed situation of the Turks to Yang Jian, who was then the regent of Northern Zhou.
He was allied with Gao Baoning (高寶寧), the former Northern Qi general who was still holding Ying Province (營州, roughly modern Zhaoyang, Liaoning).
[5] Sheng's memorial was thoroughly describing rivalries inside Turkic nobles: "Tardu, compared to Ishbara, has strong troops but a lower position.
Zhangsun Sheng himself was promoted to General of the Chariots and Cavalry (車騎將軍) and was sent through the Huanglongdao (Chinese: 黃龍道; lit.
'The Dragon Road'), carrying gifts to the Khitan, Xi, and Xianbei tribes, who acted as guides to reach Chuluohou.
According to Chinese sources - which may be exaggerated - khagan led 400,000 cavalry from Lanzhou where they defeated Daxi Zhangru's (達奚長儒) army and sought to advance further south.
Surprisingly, Tardu left his army and Ashina Rangan, who was approached by Zhangsun Sheng sent a false news about alleged revolt of the Tiele to Ishbara, causing him to retreat.
[6] Being in a civil war, Ishbara asked Wen of Sui to adopt his wife, who was originally a Northern Zhou princess.
Sheng returned with favorable results and was appointed as the General of the Left Cavalry of the Honored Guard (左勋卫车骑将军), and the Commandant of the Chariots (车骑将军).
However, he died next year too and Sheng was sent to mourn him, bringing with him the treasures looted from Chen dynasty to bestow upon Tulan Qaghan.
Sheng bribed Tulan's officials to discover Yang Qin's location, captured him at night, and presented him to khagan, exposing the Princess' conspiracy.
Khagan was forced apprehend Princess' Sogdian associate Hu Ansuijia (胡人安遂迦) and others, handing them over to Sheng.
[citation needed] Later Khagan submitted a petition requesting a new marriage in exchange, and the court was inclined to approve it.
According to Sheng, it would be better to approve his request, invite him to move south, where his small force would be easier to control, and use him as a buffer against Tulan.
Tulan started to gather invasion party to attack Sui repeatedly for two years, only to be reported to emperor beforehand by Rangan every occasion.
The emperor promoted Sheng to the rank of General of Agile Cavalry of the Honored Guard (左勋卫骠骑将军), holding a special commission over the Turks.
Zhangsun however asked for a permission to move them to Wuyuan, fortify it with the river as a defense, and dig a trench 400 li long from east to west to create a secure area for them to live and graze without fear of raids.
Tulan was assassinated by his own men in 599 and Sui dynasty moved to enthone Qimin Qaghan in his place, which was not accepted by Tardu.
Sheng was appointed governor of Xiangzhou, responsible for raising troops in Shandong and working with Li Xiong (李雄) and other generals to manage the situation.