The current automatic coal mining technology with memory cutting as the core technology cannot perceive the changes of geological conditions of the working face autonomously, and the shearer can hardly realize automatic height adjustment control according to the changes of coal seam thickness. And it is only a preliminary exploration for precision mining. In order to solve the above problems, a digital coal seam-based precision mining system for fully mechanized working face is developed. Firstly, the system establishes the initial 3D digital coal seam model by using coal mine geological data, working face cutting data and geological realistic data of the working face transportation and return air roadways and the cubic spline interpolation method. Secondly, through the fully mechanized mining equipment inertial navigation system, odometer, radar, angle sensor, the model dynamically senses the actual walking trajectory and cutting trajectory of the shearer, and dynamically corrects the established initial 3D digital coal seam model and generates the straightness detection curve of the scraper conveyor. Finally, according to the revised 3D digital coal seam model, the cutting trajectory curve of the shearer is dynamically planned and sent to the shearer control system to instruct the shearer to automatically adjust the height according to the change of coal seam thickness. Through the scraper conveyor straightness detection curve and hydraulic support travel information comprehensive analysis, the model calculates the displacement deviation of each hydraulic support for the next cut. And the displacement deviation of each hydraulic support for the next cut is sent to the hydraulic support control system of the fully mechanized working face to realize the hydraulic support automatic straightening. The test results show that the system realizes dynamic planning of cutting trajectory of the shearer, automatic tracking control of the height adjustment trajectory and automatic straightening of hydraulic support. The cutting trajectory of the shearer planning knife can be obtained through the CT slice of 3D digital coal seam model. The planned cutting trajectory error is less than 02 m. Without human intervention, the automatic cutting time is about 1 h for 250 m long working face, and the automatic cutting time for triangular coal is about 30 min.