Su Gui himself passed the imperial examination when he was young (before the age of 19)[3] and was made a military officer at Heng Prefecture (恆州, roughly modern Shijiazhuang, Hebei).
[4] When his mother died, his mourning was viewed as so deep and genuine that it got the attention of the chancellor Zhang Da'an, who recommended him for promotion, and he was made a member of the staff of Emperor Gaozong's son Li Dan the Prince of Yu.
During the reign of Emperor Gaozong's wife Wu Zetian – who seized the throne and claimed the title of "emperor" of a new Zhou dynasty in 690, interrupting Tang—Su Gui successively served as the prefect of Lang Prefecture (朗州, roughly modern Changde, Hunan) and She Prefecture (歙州, roughly modern Huangshan, Anhui).
While he was serving as a prefect, the once-powerful secret police official Lai Junchen was demoted and made a military officer under him.
Su submitted a petition to Wu Zetian suggesting that those suffering from the drought be exempted from service, and that the circuit-touring officials be recalled.
In spring 706, Su was made Shizhong (侍中) – the head of the examination bureau (門下省, Menxia Sheng) and a post considered one for a chancellor.
I cannot face the north[7] and serve him.The senior chancellor Wei Yuanzhong then defended Su's actions and further also advocated that Zheng be put to death.
Su responded to Emperor Zhongzong: I, your subject, have heard that chancellors are supposed to harmonize the yin and the yang, and govern over things on behalf of heaven.
I am foolish and not doing my job, and therefore I did not dare to carry out shaowei.Later in 709, Su was also put in charge of editing the imperial history, along with fellow chancellor Tang Xiujing.
During the meeting, the draft will was discussed, and Zong Chuke and Wei Wen, arguing that it was inappropriate for Li Dan to be co-regent, as traditionally, a brother-in-law was not supposed to speak to a sister-in-law.
Zong and Wei Wen became visibly angry, and Su did not dare to speak further, and so the provision of having Li Dan serve as co-regent was stricken from the draft will.
Su soon asked to retire, however, on account of illness, and he was removed as a chancellor and made a senior advisor to Li Longji, who was created crown prince.