To　raise　the　accuracy　of　the　fault　diagnosis　of　the　gear,　through　the　study　on　resonance-demodulation　technology　of　picking　up　the　shock　pulses,　and　combining　the　matrix　distinguishing　sieve　method　and　the　double　characteristic　analysis　method,　this　article　concludes　the　basic　diagnosis　rules　of　the　wire　rolling　mill　gear　box　based　on　analysis　of　a　great　deal　experimented　and　tested　data,　and　identification　of　twenty-one　hidden　troubles.　The　rules　have　been　applied　in　the　real　fault　diagnosis,　and　are　proved　to　work　well.