A basic structure of excavator anti shovel device is introduced. The digging resistance force graph of the rotating bucket is drawn, and the calculation method of digging resistance is analyzed. Besides, the calculation diagram of the theoretical digging force of the bucket arm cylinder is given, the calculation method of theoretical digging force of the working hydraulic cylinder is deduced. Then, the calculation diagram of the theoretical digging force of the stick is given. The calculation method of actual digging force of the stick working hydraulic cylinder is deduced. Considering the influence of the actual engineering situation on digging force of the rotating bucket, the maximum actual digging force is calculated when the bucket excavating.