Abstract: In planar near-field antenna measurements, finite scanning plane truncation is one of the main reasons which cause measurement error, therefore, the key point is to find a solution to solve the truncation error. The process of solving the plane wave spectrum from a finite field in planar near-field measurements is abstracted as a mathematical model for the band-limited function extrapolation, and it is proved that Gerchberg-Papoulis (GP) algorithm applicated in planar near-field antenna measurements is feasible, which is based on nearfield to farfield transform theory in actual measurements. This paper introduces the GP algorithm in planar near-field antenna measurement, and the effect of algorithm with different iterations is also analyzed. The results show that the differences between deduced pattern and theoretical pattern decreased significantly out of reliable angle region with the iterative number of algorithm increase. Therefore, the method introduced in this paper can significantly reduce the truncation error. Moreover, the influences of algorithm convergence brought by errors are also analyzed, the results show that the effect of the algorithm was influenced by errors greatly.