Pseudo-range and carrier phase are two basic range measurement values of receiver, which are obviously different and complementary. Pseudo-range measurement contains various errors such as clock difference, ionospheric delay and so on, but it reflects the distance between satellite and receiver. Carrier phase measurement is circumferential ambiguity, but it is very smooth and accurate. In addition, the multipath effect has much more influence on the pseudo-range than the measurement of carrier phase. At present, the industry usually adopts the Hatch filter combining the advantages of pseudo-range and carrier measurement to output smoothed pseudo-range without ambiguity and relative smooth. By setting different smoothing constant and adding ionospheric model, the smoothing results are analyzed, so as to evaluate the performance of the filter, and finally provide a decision basis for the selection of smoothing constant.