The invention discloses an automatic control system and an optimal trajectory planning method of an intelligent excavator. The system comprises a data acquiring and executing module, a network, a processor and a storage device; and the data acquiring and executing module comprises a 3D scanner, a power sensor, a proximity sensor, a displacement sensor, an angle sensor, a torque sensor, an information device, a controller, the processor, the storage device and a wireless transceiver. According to the automatic control system and the optimal trajectory planning method of the intelligent excavator, because the 3D scanner is adopted to determine the contour of the surface of a to-be-excavated material, the coordinate matrix of the contour is obtained through the processor, and therefore accurate modeling is performed on a material pile, and accurate prediction on the surface load of the excavated complex material pile is achieved. According to the automatic control system and the optimal trajectory planning method of the intelligent excavator, because the information device and the processor are used for optimizing control parameters in the excavating process of the excavator, the purposes that the excavating load is minimum, and the excavating energy consumption is lowest are achieved. According to the automatic control system and the optimal trajectory planning method of the intelligent excavator, the accuracy of a load predicting algorithm is improved, and accurate prediction on the excavating load is achieved.