Applying computable general equilibrium mod el and comparative static method，the effects on efconomic system of expanding social insurance coverage and gradually uniforming social insurance payroll tax rate are analyzed quantificationdly andwholly．Inthis veay．the effects on socialwelfare．on prod uetion．on the level and composition of final demand in production market．and on labor demand in labor market are analyzed．Then some advice is given on social insurance reform．