With the increasingly fierce struggle of electronic countermeasures in the modern battlefield, the environment of radar falls under serious threat. Radio frequency(RF) stealth technology is an important approach to improve the viabilities of radar and its platform in the battlefield. In this paper, the problem of RF stealth in airborne radar system is investigated, and a novel optimal resource management algorithm with passive sensor cooperation in airborne radar system is proposed. The sequential filtering algorithm based on interacting multiple model (IMM) and extended Kalman filter (EKF) is employed for target tracking, and the passive sensor is utilized in preference to radar. In the proposed algorithm, the comparison of the predicted state estimation covariance and the predefined threshold of covariance is used to control radar under an intermittent-working state. Furthermore, the radiation energy is adaptively adjusted to improve the RF stealth performance according to the target motion. Numerical simulation results demonstrate that the proposed algorithm can effectively configure radar working parameters and improve RF stealth performance.