Abstract-At present 33.81% China’s employees do not enjoy basic medical insurance when they are at work. This paper mainly discuss 4 key factors, the growth rates of penetration, density, involved degree and structure-againg degree, which influence fund balance performance of China’s basis medical insurance for urban employees via fund growth model and explore the possibility for involving more populations into this package. Our findings are as followed. On one hand,GDP and average premium increase would improve fund balance growth. On the other hand, involved and againg degrees have negative impacts on fund balance. The conclusion also prove adverse selection and moral hazard has reduced the effienciency of current basic medical insurance fund performance for urban employees. Keywords- China’s basic medical insurance for urban employess; fund growth model; involved rate; fund balance