Abstract: In order to avoid failures caused by the inadequate maintenance of excavator, the paper researched excavators faults happened in practice based on W K- 35 and WK- 10B excavators. It also analyzed four failures modes of gear broken teeth, gear tooth wear, gear tooth surface pitting and gear shaft fracture by the anal ysis method of failure tree, the specific reasons of gear failure was got. It was also indicated the preventive measures from the aspects of excavator and its correspondi ng parts procurement, gear lubrication, oil monitoring, and others, after the actual application, it showed that these preventive measures for reducing the gear lubricatio n oil monitoring of excavator gear was effective.