The invention discloses an error detection and separation method of a high-precision laser measurement system. Total errors include laser beam drift errors of high-precision laser measurement and measurement system structural errors, wherein the laser beam drift errors comprise flat floating, angular floating and random drifting of laser beams. The errors refer to micro deformations generated by the fact that the system structure and tools are affected by the environment. Accuracy and stability of laser precision measurement will be seriously affected. According to the invention, by establishing a mathematical mode of the laser measurement system errors, and using a special device combining a laser source and a four-quadrant detector, the total errors of the high-precision laser measurement system are detected, and the laser beam drifting errors and the system structural errors are calculated and separated.