An Chonghui
In 928, Fan was made one of Li Siyuan's chiefs of staff ("Shumishi"). He was soon thereafter made the military governor of Chengde Circuit (成德, headquartered in modern Shijiazhuang, Hebei). He was also given the honorary title of acting "Taibao" (). He was apparently subsequently recalled to the imperial government, for, as of fall 930, he was referred to as the "former" military governor of Chengde without being referred to by other titles. At that time, Li Siyuan was considering replacing then-chief of staff An Chonghui (who was the most dominating figure at court for Li Siyuan's entire reign up to that point) due to accusations that An was overly domineering of the political scene. Fan urged against removing An, and when Li Siyuan responded, "Can you not do so?" Fan responded, "I, your subject, have not served you as long, and I am not as talented as An Chonghui. How would I dare replace him?" Li Siyuan subsequently kept An as chief of staff, but also made Fan a chief of staff, serving with An. After An was finally removed (and subsequently killed) in 931, Zhao Yanshou, also a son-in-law of Li Siyuan's, took over as the other chief of staff, serving with Fan. Nevertheless, it was said that because An had suffered his fate due to his domination of the political scene, neither Fan nor Zhao dared to overly involve themselves with policy decisions, such that the eunuch Meng Hanqiong (who took over as the director of palace affairs), and Li Siyuan's favorite concubine Consort Wang, became highly influential in policy decisions. In fall 931, Fan was given the designation "Tong Zhongshu Menxia Pingzhangshi" (), thus also designating him as a chancellor.