Abstract: Initiated by n-BuLi in n-hexane, the anionic homopolymerization of AN has been studied. The results show that the molecular weight of PAN is independent of the concentraion of n BuLi and is increased with the increase of AN concentration. The AN conversion could reach 80% of the ultimate conversion in a few minutes. It has been found that EO-cap and VP-cap deactivation could reduce parts of side-reactions and a formula for estimating initiator efficiency is suggested. Analysing by GPC and IR graphs of PAN obtained, we have discussed the effect of reaction conditions on side-reactions of AN polymerization.