Internal recycling continuous sand filter, a new integral water treatment facility is a sand washing circulation system based on the theory of micro flocculation, and the continuous filtration process is just an integration of filtration and backwash. The process parameters having effect on the working efficiency of the new filter are discussed under the following conditions: size of filter material (0.7~1.0 mm)? thickness of filter bed(0.6 m)?filtering velocity(12 m/h)?ratio of gas to water(9~11),and sand recycling velocity(2~4 mm/min).