The invention discloses a real-time vehicle trajectory predicting method and device based on radar detection data. The real-time vehicle trajectory predicting method includes the steps that accordingto the data collected by a vehicle sensor and a radar in real time, the absolute velocity and direction of a target vehicle and the included angle and the included angle change rate of the velocity direction between a vehicle and the target vehicle are calculated, and then the yaw velocity of the target vehicle is calculated through the included angle change rate and the yaw velocity of the vehicle; the turning radii of the vehicle and the target vehicle are calculated by using the velocities and the yaw velocities of the vehicle and the target vehicle correspondingly; and finally, travellingtrajectories of the vehicle and the target vehicle are predicted, and the trajectory of the target vehicle is transferred into a vehicle coordinate system of the vehicle to be calculated through the relative distance and the included angle of vehicle coordinate systems of the vehicle and the target vehicle. The real-time vehicle trajectory predicting device comprises the radar, a vehicle-mounted sensor, a controller and an actuator. The real-time vehicle trajectory predicting method and device based on the radar detection data has the advantages that the travelling trajectory of the vehicle and the travelling trajectory of a target object in the environment can be predicted accurately and in real time, collision danger is judged timely, and safety and stability of vehicle travelling are improved.