In view of the localization that the optimal examining item did not change any more once confirmed in the conventional optimizing model for the checking period of repairable device, a dynamic realtime control strategy was proposed for the checking rate by the device state according to the reliability theory and the linear control theory. The lifecycle model of repairable device was established, and the system steadystate reliability and the mean time to failure (MTTF) were given out. The dynamic control strategy on the checking rate was presented and its adaptability was analyzed. The aim was to modify the MTTF of device to reduce the possibility of corrective maintenance intervention, and accordingly reduce the maintenance examination cost farthest. The state of device was estimated. The dynamic control time spacing and the strategy were given out, as well as the probability distribution of checking rate. Results indicate that the strategy is effective to improve the maintenance decisionmaking quality and ensure the products working under the most suitable state.