Abstract: Gyratory crushers are characterized by advantages such as evenly distributed grain size,high crushing efficiency and big crushing ratio,and widely applied to ore crushing systems.The crushing system in the Phase 2 Project of Pacific Mining Co.,Ltd.employs KB 54-75 gyratory crushers that are complex in structure and have a great many inner parts.The paper analyzed the structural composition,working mechanism and common malfunction as well as their countermeasures about the KB 54-75 gyratory crushers,and   introduced in detail the daily maintenance measures,repair cycle and precautions,which ensure normal operation of gyratory crushers,improve the working efficiency of ore crushing production line and save maintenance cost.