The invention discloses a robot positioning precision evaluating method based on monocular vision. A calibration plate is arranged at any position in a robot motion space, in the motion process, a robot observes the same calibration plate for many times at the different positions in the working environment of the robot, multiple times of sampling is conducted through an observing method in this way, and according to all observing information collected in the one-time motion process and statistical characteristics of the observing information, quantitative comparison of the positioning precision of different positioning algorithms in the same working environment is realized. According to the robot positioning precision evaluating method, the real position and posture of the robot are obtained without other precision instruments, a large number of repeated experimental tests are not needed, and the working efficiency is improved while the using cost is saved; in addition, the calibrationplate with the unknown environmental position and posture is adopted, thus the evaluating method is simpler and more convenient, and the motion environment and the motion space of the robot are not limited; and finally, the precision of a robot positioning algorithm is described by expression positively correlated with the positioning error, and the positioning precision between the different algorithms is compared.