In order to improve the solid particle separation performance of the separator, the effects of liquid level, inlet liquid flow rate and particle size on the separation efficiency of solid particles in horizontal separator are studied by single factor and orthogonal experiments.The results show that the separation efficiency of solid particles with particle size larger than 65 micron is higher, and the influence of liquid level height is not obvious;with the increase of liquid level height to 0.5D, the separation efficiency of solid particles in horizontal separator is improved. When the mass separation efficiency is less than 60 L/h, it gradually increases to 90%;the median particle size of the outlet is relatively stable at 6-18 um;the influence of three variables on the separation efficiency is in turn: particle size > liquid level > inlet liquid flow rate;the particle size is the most significant effect at the significant level of a=0.05.