Abstract: In order to study the flow state of non-Newtonian fluid in lobe pump, three-bladed cycloid lobe pump was selected as the research object, and the internal flow of the lobe pump under pig manure with different gas phases and solid particles was calculated by numerical simulation. The results of the analysis show that: bubble diameter, solid phase concentration and particle diameter have little influence on the pump performance , while the apparent viscosity and power law index have a greater influence on its performance. Among them, with the increase of the power law index, the flow pulsation coefficient is increased, so the operating stability of rotary lobe pump will be reduced to a certain extent. With the increase of apparent viscosity, the average flow rate and volumetric efficiency gradually increase, and the pulsation coefficient gradually decreases, which will increase the operating stability of rotary lobe pump to a certain extent. The results of the study laid the foundation for the optimized design of rotary lobe pump when delivering non-Newtonian fluid.