The invention relates to a hydraulic (semi-automatic) automatic screen replacing device of a plastic extruding machine. The hydraulic (semi-automatic) automatic screen replacing device is characterized by comprising a walking lifting platform assembly, a space positioning table assembly and a hydraulic rotating arm assembly; the walking lifting platform assembly is composed of fixing trundles, table leg frames, a hydraulic oil cylinder, a base, a lifting rotary handle, lifting guide rails and a threaded lifting column; the space positioning table assembly is composed of a cross-shaped workingtable guide rail a, a linear guide rail, a first stepping motor, a motor frame, a coupler, corner fixing plates, a second stepping motor, a cross-shaped working table guide rail b and a third steppingmotor; and the hydraulic rotating arm assembly is composed of a wrench socket, a fixing disc, a guide rail sliding block, a lead screw, a hydraulic wrench oil inlet and outlet, a hydraulic wrench andphotoelectric positioning sensors. According to the hydraulic (semi-automatic) automatic screen replacing device, the problems that the working environment temperature is high and the labor intensityis high when a filter screen of the plastic extruding machine is manually replaced, and raw materials are wasted due to the fact that fluorine plastic is solidified in the shutdown period are solved,so that the (semi-automation) automation of filter screen replacement of the plastic extruding machine equipment is realized.