The invention relates to a hydraulic system of a hydraulic drawing press. The hydraulic system comprises a main cylinder, a hydraulic cushion cylinder, a two-position four-way reversing valve, a three-position four-way revering valve, a back pressure valve, an oil inlet main pipe and an oil return main pipe. The main cylinder is vertically arranged, a piston rod of the main cylinder is downward, and a slide block is arranged at the lower end of the piston rod of the main cylinder. The hydraulic cushion cylinder is located below the main cylinder, and a piston rod of the hydraulic cushion cylinder is upward. The back pressure valve is provided with an inlet and an outlet. The outlet of the back pressure valve is connected with an oil tank through a pipeline. A damping opening is formed at the portion, corresponding to the inlet, of one side of the back pressure valve. The damping opening is connected with a third oil outlet of the three-position four-way reversing valve through a pipeline. The repetition accuracy and the appearance quality of workpieces machined through the hydraulic system are high.