This paper is research on Hofmann degradation to prepare polyvinylamine (PVAm) . Material ratio, reaction temperature, addition mode and other reaction conditions which have effect on amination degrees were discussed as well as recycle of the mixed solution containing alcohol and base. Results show that the amination degrees of product is 84.54% by using Commercial nonionic polyacrylamide (PAM) , the base solution recycling from the mixture can be used 3 times. In this modified Hofmann degradation,polyacrylamide was added into NaClO and NaOH solution direactly to make chloro- polyacrylamide, then put it into base solution,in order to increase yield per volume solution.