A multi-modality evolutionary Rao-Blackwellized particle filter(MERBPF) algorithm is proposed for mobilerobot fault diagnosis of dead reckoning system. The inconsistency from particle degeneration problem is solved by integrating swarms’ intercross and mutation strategy and adding disturbance factors accoding to diversity. Robot moving states are determined by expert rules reasoning mechanism and monitored by each different ERBPF. Finally, the multi-modality ERBPF is formed, which expresses complex logic clearly. The experimental results show that MERBPF maintains a strong robustness even under the strong process noise, which improves the accuracy for the fault diagnosis of robot’s dead reckoning investigation system.