The invention relates to a solid-liquid separation processing method for tiny insoluble matters in acidic slurry and belongs to the technical field of chemical engineering and technical solid-liquid separation. The solid-liquid separation processing method is a processing method for separating the tiny insoluble matters from the acidic slurry, and is characterized in that two types of flocculation agents are added dropwise, and by adjusting the circulation volume of an acidic clear liquid, the solid-phase concentration of the acidic slurry entering into a settling separation system is automatically controlled while the viscosity of the acidic slurry is reduced, wherein the adopted inorganic flocculant is polymerized ferric sulfate; the organic flocculant is polyacrylamide; the solid-liquid separation temperature of the acidic slurry is 20-65 DEG C; and the viscosity of the acidic slurry is 20-300mPa.s. By using the solid-liquid separation processing method, the purposes of reducing the viscosity of the acidic slurry, improving the settling property and increasing the separation efficiency are achieved by automatically adjusting the solid-phase concentration of the acidic slurry entering into the settling separation system by virtue of adjusting the circulation volume of the acidic clear liquid. A proportional control device is used as a coagulation flocculation agent adding system, thereby automatically controlling the flux of the added agent according to the flux of the acidic slurry. A coagulation flocculation agent solution is prepared by using the acidic clear liquid, thereby maintaining the water balance of the system.