This paper investigates this changing pattern of health insurance coverage in China using panel data from the China Nutrition and Health Survey (1991?2000). It is the first attempt in this literature that tries to identify precisely the effects of specific policies and reforms on health insurance coverage in the transitional period of China. The fixed effects linear model clustering at the province level is used for estimation, and results are compared to alternative models, including pooled OLS, random effects GLS model and fixed effects logit model. Strong empirical evidence is found that unemployment as a side effect of the Open Door Policy, and the deregulation of SOE and collective enterprises were the main causes for the decreasing trend. For example, urban areas that were highly affected by the Open Door Policy were associated with 17 percentage points decrease in the insurance coverage. Moreover, I found evidence that the gaps between SOE and non-SOE employees, collective and non-collective employees, urban and rural employees have considerably decreased during the ten years.