Abstract: In order to improve the accuracy of localization, the paper applies particle filtering to fuse WiFi fingerprinting and pedestrian dead reckoning (PDR). The map matching algorithm. The map matching algorithm first makes use of the indoor map to constrain the improper transitions of particles to reduce wall-crossing problems of them and then corrects wall-crossing problems of trajectories with a trace-back method. Evaluations show that the trajectories of the fused solution are closer to the real trajectories than WiFi fingerprinting and PDR, and after map matching the trajectories are more accurate and reasonable.