The utility model relates to a rotary piston pump which is characterized in that a blocking plate is composed of a slide plate frame which is inserted in a bar hole at the top wall of a pump body and is in a shape like the Chinese character 'ao', and a slide plate which is corresponding to the slide plate frame and is in a shape like the Chinese character 'ao'; a sliding friction mechanism or a rolling friction mechanism is arranged between the slide plate and the slide plate frame; the outer part of a rotary piston is provided with a lining sleeve, both sides of which are respectively provided with a lining plate; the slide plate and the slide plate frame are positioned in an axial opening of the lining sleeve and an opening groove of the lining plate; the inner part of the pump body can be provided with two same coaxial rotary pistons or two groups of same coaxial rotary pistons, circular cylinders which are respectively corresponding to the rotary pistons, a blocking plate, a lining sleeve and a lining plate. The utility model has the advantages of reliable performance, long running time, little energy consumption, high efficiency, low cost and easy fabrication.