Traditionally, the peak overpressures of multi-point shockwave are obtained through the sensor array by using the electrometric method, and then the surface interpolation is carried out by the mathematical model to draw the contour lines of the shockwave overpressure field. The cross-validation method of the mean absolute error (MAE), mean relative error (MRE), and root mean square error (RMSE) was proposed in this study to achieve high precision and effective interpolation of the contour lines. The quantitative test of Kinney-Graham Formula was verified, and the peak overpressures of the multi-point shockwave of a 7.62-mm caliber gun and a naval gun were obtained through the sensor array based on polar coordinate. Then, the shockwave overpressure field was interpolated by the inverse distance weighted (IDW) interpolation, the ordinary kriging interpolation(OK), the radial basis function (RBF) interpolation, and the cubic spline (CS) function interpolation, Finally, cross-validation analysis was performed on MAE, MRE, and RMSE. Results demonstrate that the MAE of the RBF interpolation is 0.038, and the MRE is 0.001. The error is smallest, the accuracy is highest, and the interpolation effect is closest to the shockwave field model. The OK interpolation is close to the RBF interpolation. The MRE of the CS interpolation is 0.254, which is relatively large. The RMSE of the IDW interpolation is 14.268, which is abnormal. The RBF interpolation is the optimal interpolation algorithm for the shockwave overpressure field, which provides a reference for the contour drawing of the shockwave overpressure field.