Abstract: A rapid detecting method based on target validity was proposed to improve detecting performance of cut-in target using vehicular radar. The Kalman prediction was used as the judgment criterion of targets validity which could be represented by valid probability. In consequence, by extending the searching range to sidelines and setting up an inheritance mechanism of valid probability, the detection rate of the cut-in target was quickened. The experiment results show that the proposed rapid detecting method is robust and it can remove the disturbance caused by roadside objects or false signals. Moreover, the real-time performance of detecting cut-in target is improved obviously.