Abstract: In single point positioning,the accidental errors such as multipath effect and receiver noise have a great influence on the accuracy of positioning, and it is difficult to select a fixed model to weaken it. In view of the above problems, analyzes the principle of wavelet analysis from the signal structure and error source of GPS, and uses the discrete orthogonal wavelet db3 to denoise the GPS observation C1.The experiment shows after the observed values are processed using the method described above, the accuracy of positioning can be improved by 31.93％ in the period when the quality of the observed value is bad, and the positioning accuracy can be increased by 16.02％ in the period when the quality of the observed value is good.