Iterative closest contour point(ICCP) algorithm was applied into map aided navigation, in which simplex algorithm was used to estimate the optimal trace of vehicle. However, simplex algorithm was usually convergent at the local optimization so that there was mismatching or even diverging. The rule of mismatching judgment for ICCP was established to reduce mismatching probability. The rule of mismatching judgment for ICCP was established by probability data association filter(PDAF). Simulation shows that PDAF improves the convergence and precision compared with the ICCP algorithm without mismatching judgment, and its mismatching probability decreases 30 percent compared with M/N method. The PDAF method for mismatching judgment increases precision and stabilization.