3D human motion analysis system is gaining more and more popularity and importance in sports training, game simulation and many other areas. Particle filter algorithm, as a powerful optimized method, can be applied to 3D human motion analysis system with more accurate results delivered and assured. An improved (hybrid) particle filter algorithm (IPFA) is proposed in this paper which integrates the advantages of partitioned particle filter algorithm (PPFA) with annealed particle filter algorithm (APFA). The results show that, the hybrid algorithm (IPFA) gives rise to more accurate results with less computational time consumed, compared to PPFA and APFA, and improves tracking efficiency and accuracy of 3D human motion substantially.