Abstract: Using the actual data collection,the quality of L2 carrier phase is analyzed in two respects,which are SNR and the positioning residual error.Some conclusions are given.Firstly,the SNR of L2 carrier phase resumed by L2 C code is improved obviously,almost close to the SNR of L1 carrier,with a difference of less than 5 dBHz.Secondly,it has a more stable SNR than that obtained before GPS modernization.Meanwhile,the positioning residual error is smaller than L2 carrier phase without L2 C code,which can significantly improve positioning accuracy.