To detect the bias fault in stochastic non-linear dynamic systems,a new Unscented Kalman Filtering(UKF) based real-time recursion detection method is brought forward with the consideration of the flaws of traditional Extended Kalman Filtering(EKF).It uses the UKF as the residual generation method and the Weighted-Sum Squared Residual(WSSR) as the fault detection strategy.The simulation results are provided which demonstrate better effectiveness and a higher detection ratio of the developed methods. To detect the bias fault in stochastic non-linear dynamic systems, a new Unscented Kalman Filtering (UKF) based real-time recursion detection method is brought forward with the consideration of the flaws of traditional extended Kalman Filtering (EKF) .It uses the UKF as the residual generation method and the Weighted-Sum Squared Residual (WSSR) as the fault detection strategy. The simulation results are provided which demonstrate better effectiveness and a higher detection ratio of the developed methods.