The power-shift steering transmission on tracked armored vehicle works in a harsh environment.The lubricating oil may be mixed with lots of wear particles.The wear particles into the planetary gear with the lubricating oil will lead to the premature wear of the gear, and affect the reliability of the transmission.By analyzing the wear particles movement and the force the particles endured during the movement procedure, the model of the influence of particles introduced force(PIF) on the transmission components of the planetary gear was established, the regulation that the wear particles influence the lubrication of needle bearing was obtained by analyzing the parameters in the model with simulation.The design of related structure and its maintenance were suggested based the point of view to reduce the friction of moving pairs.The research results show that the PIF is increased first and then decreased along with increasing of minimum film thickness, is rapidly enlarged along with increasing of diameter of particles, and is enlarged along with increasing of radius of needle of needle bearing, but the speed of increasing is slowed down.