In order to investigate the efficiency of attitude determination system using particle filter. The system state equation and measure equation of a satellite with star-sensors and gyros were established. And particle filter was used to estimate the attitude of satellite. The simulation results showed that the system can convergent not only for the small initial estimation error, but also for the big initial estimation error. But EKF can convergent only for the small initial estimation error. Finally, the effectiveness of PF applied to the gyro-free mode was also verified.