Abstract: Aiming at the shortcoming that integrated device of electric coal drill easily fault,specially its electronic plug-ins, the paper diagnosed the fault of electronic plug-ins of integrated device of electric coal drill using fault-tree analytical approach, established a fault-tree model of electronic plug-ins, designed program of fault diagnosis,and made detailed diagnosis and analysis taking two faults as examples that the faults were refusing action when short-circuit protection and the electronic drill couldn’t start.