We study the synthesis of 9, 9-bis (4-aminophenyl) fluorene(BPF) and the effects reaction conditions such as different acid catalysts, mass of acid catalyst, mass of aniline, reaction temperature and reaction time on the yield of BPF were discussed. The test results showed that dehydarted by appropriate amout of toluene when n(aniline):n(HCl):n(fluorenone)=10:1.5:1, reaction temperature is 130 ℃, reaction time is 6 h, we can gain the highest rate of BDF to 88.3%.