Abstract: According to the slow convergence of precise point positioning(PPP) in noisy environment, a partial ambiguity fixing（PAF）method was proposed based on LAMBDA algorithm, and then the ambiguity subset with constraint of maximum success rate and Ratio value was defined according to the basic idea of the more accuracy for the float solution, the easier for right fixing. Finally, the validity of PAF method for PPP fixed solution was analyzed in terms of the reliability of ambiguity fixed, convergence speed and positioning accuracy. The results show that the performance of precise point positioning is improved by the PAF method. Compared with traditional method, the convergence time of ambiguity resolution is shortened by about 1/4, and the reliability is increased by almost 2 times. Especially for less measurement information in the initialization stage or lager residual error in which it is difficult to fix all the ambiguity, a higher accuracy for PPP fixed can be quickly obtained solution by PAF method.

Key words: Precise point positioning, Ambiguity fixing, Ambiguity subset, Global navigation satellite system