When the train passes the curve, the excessive swing angle of the coupler will seriously threaten the safety of the train. Therefore, the coupler angle must be checked when the train passes through curves. In this paper, the attitude position of the front and rear vehicles was given by analytical method, and the swing angle of the coupler was solved according to the relative position of the coupler. Finally, according to the algorithm, the swing angle of the coupler was calculated when the train passed through the horizontal curve and the vertical curve. It showed that under different working conditions, the maximum swing angle of the coupler appeared when the front and rear center pins of the two cars were in different directions. Under the curve-line working condi tion, the maximum swing angle of the coupler appeared when the two trains just entered the curve; under the Scurve condition, the maximum swing angle of the coupler appeared after the first position train completely entered rear curve and the center pin of the second position train was located in the line; under the condition of the vertical curve, the maximum swing angle of the coupler appeared at the slope point.