According to the feature that the measurements of the same target at the same time have spherical shape, an algorithm of track initiation based on adaptive K-means clustering and modified logic-based approach is proposed in this paper. The improved K-means clustering algorithm can determine the cluster number and the initial cluster centers adaptively. Then the center of each cluster is found and taken as the measurement of the targets at this moment. By doing so, the track initiation process is simplified. According to the target’s movement characteristic, a modified logic-based method is used to initiate the target track. Simulation results show that the improved K-means clustering algorithm can recognize the number of targets correctly and the recognized targets are close to the true targets; the modified logic-based approach can effectively suppresses clutter and reduces the probability of false alarm.