In order to effectively improve the detection accuracy of the radar, a calibration method based on fitted partitioning under non-uniform distribution of system errors is proposed.Firstly, spatio-temporal alignment between the marine multi-target information obtained by the radar and the truth data provided by Automatic Identification System (AIS) as well as correlative processing are carried out, and the error sequence is obtained.Furthermore, the assumption of system error distribution based on two non-uniform distribution modes is given.On the basis of the rationality of the assumption, the coverage area of radar detection is divided by fitting processing.The estimated value of system errors is obtained, and it is used for the calibration of the radar.Finally, the experiment proves the effectiveness of the method.