A new path planning method was proposed for an excavator to finish the autonomous mining, which was aimed to make the trajectory smooth and continuous, and decrease vibration impact strength. According to the proposed method, the path in working space will be reasonably segmented, so that the calculation of the amount of calculation will be reduced as far as possible in order to ensure that the path deviation of the path planning result is not affected by the task completion, and the trajectory planning of each segment was computed respectively by using interpolation polynomial with variable order. A certain type of single bucket hydraulic excavator was taken as the research object. First of all, the mining path was separated into five segments which employed interpolation polynomial with high order of 3—3—5—3—3 successively in trajectory planning. The simulation was achieved by Matlab software. The result showed that the three curves for joint angle, angular velocity and angular acceleration were smooth and continuous, but some acceleration values in some segments exceeded the acceleration constraint. In order to improve the dynamics performance of the excavator’s working mechanism, the segments having odd values were computed afresh with modified trajectory polynomial of which the highest order was calculated in terms of the acceleration constraint. New curve which figured by the piecewise polynomial with variable order showed that the new trajectory planning could be of use for the stable and continuous operation in autonomous mining.