Despite Sun's high status, little is firmly established about his career except for the time that he served as chancellor—as, unusual for a chancellor, he did not have a biography in either the Old Book of Tang or the New Book of Tang. He was not even listed in the table of the chancellors' family trees in the New Book of Tang for the Sun clan, and therefore, nothing is known about his family tree.

In spring 696, Sun was serving as the acting minister of defense (夏官尚書, Xiaguan Shangshu), when Wu Zetian gave him the designation Tong Fengge Luantai Pingzhangshi (同鳳閣鸞臺平章事), making him a chancellor de facto.

In late 696, there was a treasonous plot by the officials Liu Sili (劉思禮), Qilian Yao (綦連耀), and Wang Ju (王勮) -- as the conspirators believed that Qilian was fated to be emperor one day. The official Ji Xu heard of the plot and relayed it to the secret police official Lai Junchen, who in turn reported it to Wu Zetian. Wu Zetian had Wu Yizong (武懿宗) the Prince of Henan (the grandson of her uncle Wu Shiyi (武士逸)) investigate, and Wu Yizong, promising Liu that he would be spared, had him implicate as many officials as he could, and Liu implicated some 36 officials, including Sun, fellow chancellor Li Yuansu, and other officials Shi Baozhong (石抱忠), Liu Qi (劉奇), Zhou Bo (周譒), and Wang Ju's brothers Wang Mian (王勔) and Wang Zhu (王助). All 36 households were slaughtered on the same day, and some 1,000 related persons were exiled.

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696年四月，時任檢校夏官侍郎（兵部侍郎）的孫元亨被任命為同鳳閣鸞臺平章事。明堂縣尉吉頊、合宮縣尉來俊臣密告箕州刺史劉思禮、洛州錄事參軍綦連耀、鳳閣舍人（中書舍人）王勮謀反。河內王武懿宗（武則天伯父武士逸的孫子）命劉思禮牽連朝廷官員，說這樣可以免死。劉思禮誣告鳳閣侍郎（中書侍郎）同平章事李元素、孫元亨、知天官侍郎事石抱忠、劉奇、給事中周譒及王勮的哥哥涇州刺史王勔、弟弟監察御史王助等，共三十六家，萬歲通天二年正月廿四（696年12月26日），全被滅族。