The effect of polymerization method on physical properties (viscosity and pH) of polyamine, which is widely used as a polymer coagulant, was studied. Diethylenetriamine (DETA), triethylenetetramine (TETA), epichlorohydrin (EPI) were used as monomers in this study. Addition of EPI into a dilute solution of DETA (or TETA) with deionized water is a well-known method to synthesize the polyamine. However, as a large amount of EPI is required in the general method, the residual of EPI, after polymerization, may function as a toxic contaminant in the polymer. A lesser amount of EPI could be used if the addition order of monomers is changed, i.e., when DETA (or TETA) is added to the dilute EPI solution with deionized water. The viscosity of polyamine synthesized, using this method, was about 800 cps and pH range was 8.56~9.22. On the other hand, TETA, which has four amine groups, had a better reactivity with EPI and less sensitive to the reaction condition than DETA, which contains three amine groups. From these results, a new polymerization method was proposed to minimize amount of EPI required.