When the small jaw crusher working, belt and belt pulley are driven by a motor. The movable jaw moves up and down via eccentric shaft. The angle between fixed jaw and movable jaw becomes smaller when the moving jaw runs down, then the materials are crushed into pieces. It becomes bigger when the movable jaw runs up. The movable jaw plate leaves the fixed jaw plate under the action of tension rod and spring , then the end products come out from the crushing cavity.