The restoration and the reconstruction after the Wenchuan earthquake shows that Chinas social assistance to serious natural disasters has yielded some successes, but there still exists a lot of problems. For example, perfect social donation mechanism is absent. The development of social organizations is bound by multiple factors including system and resource. Volunteers rights are lack of protection, and they do not have professional skills, etc. In response to these deficiencies, this paper discusses the construction route for social charitable assistance mechanism, incentive mechanism and coordinative mechanism, hoping to improve the social assistance system of serious natural disasters, and promote a healthy and stable development of the society.