Investigating the synchronic structure of Daoist Culture without considering any concreteness on the historical situation, we find that all Daoist believers will face the confusion and test of ethics of belief. As far as immortal belief is concerned, Daoism usually advocates skeptical and experimental spirits, and actually take an simple incomplete evidentialist doctrine of Ethics of Belief, which was first put forward clearly by morden Daoist leader Chen Ying-ning. As far as Dao belief is concerned, Daoism takes an opposition of fideism and presupposes a right of the will to belief as monotheistic religion. And the dialectic contradiction between belief and reason in Daoism has an direct influence on the interaction between Daoism and ancient mathematics and natural science.