Abstract: Time To determine the mathematical model of GPS positioning error data. Methods Time series procesing method was used to analyze the initial data,while period graph technique used in extracting the periodic error and Box-Jenkins method used in modeling the stable stochastic process Results The model can be used to improve the GPS positioning precision. Conclusion The GPS positioning error belongs to unstable time series process, composed of periodic process and stable stochastic process. The most hidden-period existing in the periodic process is 10 min and the stable stochastic processbelongs to AR ( 1 ).