A three-dimensional track initiation algorithm was proposed based on combinatorial Hough transform and traditional method to solve the problem about 3D radar track initiation. First the measurement data was projected on three planes then the combinatorial Hough transform was used to the points on three projection planes respectively. When the same point trail was initiated successfully in two projection planes at least after comparing the results on the three projection planes the straight-line track initiation was judged successfully. In the data processing, the real track initiation probability was increased using the three-step combination method and a plane kinematics speed was used to depress the combination number and reduce computational complexity greatly. Simulation in allusion to precise approaching radar data characteristic shows the effectiveness of this algorithm.