Abstract: In order to improve the viability of MIMO radar in electronic warfare, the relationship between radar parameters and its searching performance as well as the Radio Frequency (RF) stealth performance is firstly analyzed. An RF stealth optimization model considering both the intercept factor and the searching frame period is formulated for MIMO radar in searching mode. Based on the above model, an optimization algorithm of RF stealth for MIMO radar in searching mode is introduced, where the sub-array number, signal duty cycle, dwell time and searching frame period are controlled adaptively to optimize the RF stealth performance under the constraints of detection performance and time resource of the system. Simulation results show that with RF stealth algorithm in searching mode, MIMO radar can achieve desired detection performance and obtain better RF stealth performance compared with traditional phased array radar.