Based on the World Values Survey (2005-2006), this paper makes a comparison between the impacts of religions on political attitudes in China and Taiwan. Responding to the theory of the compatibility between Christianity and Democracy, this article examines the theory's applicability to China and Taiwan by using Christians as the reference group. The major findings of this paper are: firstly, considering different temporal and spatial contexts, the compatibility theory needs modification, that is, Christians are not necessarily more democratic than other religious believers. Secondly, in Chinese societies, Buddhists' commitment to democracy is no lower than Christians'. Lastly, as compared to Chinese Christians, most Muslims are more interested in politics, more positive about the society's democratic level and human rights condition. Also, they take more pride in their identity as Chinese. Yet, unlike Taiwanese religious believers, whether Chinese believers may turn these political attitudes into an engine of democratization depends on the different definitions that cross strait religious believers have hold toward democracy.