Abstract: In order to improve the radar's ability of radio frequency stealth, the relationship between phased array radar and the Radio Frequency stealth performance is analyzed. Then A novel design method of sampling period based Radio Frequency Stealth for radar target tracking is proposed based on interacting multiple models tracking algorithm, the sampling period is designed adaptively according to the target state. Firstly, desired covariance is set for the target in tracking algorithm and then each model sampling period is computed using covariance control method. Then the next sampling period is obtained by using weighted sum of the sampling period of each model by the update-probability of model. Comparing the proposed algorithm with the fixed sampling period and tradition formula method, the simulations show that our method can not only have good tracking accuracy, but also increase the sampling period which can improve the radar's ability of radio frequency stealth.