A method for detecting and compensating the swing angle deviation of a 3-PRS parallel structure CNC machine tool is proposed. The probes fixed on the machine tool worktable are used to pair two standard ball heads with different lengths and the same diameter installed on the spindle. The coordinates are collected, the machine tool swing angle deviation is calculated and obtained, and the calculation result is automatically written into the machine tool compensation file, which replaces the manual detection and compensation of the swing angle error of the parallel machine tool, improves the accuracy and reliability of the detection data, and improves the automation of flexible production. Degree.