Abstract: In order to improve the measurement accuracy of the characteristic parameters of a circularly polarized antenna, the linear polarization component method often needs to measure the linear component field several times. The interpolation algorithm is introduced into the antenna test system to reduce sampling points and improve the test efficiency of circularly polarized antenna. Radial Point Interpolation Meshless (RPIM) technique is introduced into the parameter synthesis algorithm of circularly polarized antenna. First, the RPIM technique is used to fit the amplitude and phase of the test field, and then the axial ratio and pattern of the circularly polarized antenna are synthesized in an analytic method. The performance of the algorithm is compared with the Model Based Parameter Estimation (MBPE) method based on piecewise linear interpolation technique and the Moving Least Square (MLS) method based on cubic spline interpolation, the numerical experiments show that when the sampling points are 4% of the test points, MLS fails, and the errors of MBPE and RPIM are at the order of 10-3 , when the sampling points are reduced to 2% of the test points, both MBPE and MLS fail, although the errors of RPIM increase to the order of 10-1 , it remains stable. The numerical experiments show that RPIM outperforms the other two algorithms in the case of a small number of sampling points.