This paper presents and realizes a digital filtering method for odometersignal based on state machine. The method, taking field programmable gate array as hardware，detects and filters burr of the odometer signal after resistanceCapacitance circuits and optical coupler, analyzes the causes of bring on metastable state when odometer signal is in fluctuation, gives out a design and implementation of filtering state machine and the method treating with the anomaly state caused by metastable state. The simulation results show that the method can filter out disturbance signal effectively and the counting number of odometer signal is accurate, and this is feasible in engineering.