The adjustment method of fuel supply advance angle of diesel engine is as follows: 1. If the timing gear assembly mark is correct, it is necessary to unscrew the fastening nuts of three bolts on the high-pressure oil pump, and then remove the high-pressure oil pump; 2. If the oil supply is too late, the gasket will be reduced, and the gasket will be added too early. Depending on the angle of advance and lag, the thickness of the gasket will increase or decrease. Generally, the gasket with a thickness of 0.2mm will increase or decrease, and the oil supply advance angle will change by about 3; 3. If all the gaskets are removed and the oil supply advance angle is still too late, you can cut 1 ~ 2mm metal from the oil pump body with a lathe according to the delay degree, and then adjust the correct and appropriate oil supply advance angle by adding or subtracting gaskets.