This paper introduces a new motion capture system for recovering 3D models of multiple persons separately and robustly against occlusion in real-time. Various markerless motion capture systems using video cameras have been proposed so far. However, in case that there are multiple persons in the scene at the same time, it is quite difficult to reconstruct a precise 3D model of each person separately due to the occlusion between them. To deal with this problem, the Fast Level Set Method is utilized in the proposed system for integrating stereo range data which is captured by multiple stereo cameras located around the target people. To reconstruct precise 3D models in real-time, the proposed system is implemented on a PC cluster with seven PCs and four stereo cameras. Tracking experiment of multiple persons and real-time reconstruction of 3D human models using the proposed system are successfully carried out.