This paper introduced the working mechanism and structure of three drainage devices about the ceramic filter dewatering system, improved the design according to the shortcomings of drainage device, illustrated the improved design points and working mechanism of automatic drainage device. Through contrasting, analyzing and practical application proves, the improved automatic drainage device have stable performance, low failure rate and lower cost, suit for the application of modern filter. At last, further research directions of ceramic filter were pointed out , which provided reference for the development of it