An　improved　mathematical　model　of　a　piezoelectric　vibrating　gyroscope　is　constructed　with　the　effects　of　electromechanical　coupling　and　rotary　inertia　taken　into　account.　The　gyroscope　consists　of　a　cantilever　beam　with　tip　mass　attached　to　its　free　end.　The　piezoelectric　materials　are　adhered　to　the　four　surfaces　of　the　rectangular　beam.　By　using　two　Euler　angles　and　extended　Hamilton＇s　principle,　the　electromechanical　coupled　partial　differential　equations　governing　the　flexural-flexural　motions　of　the　piezoelectric　gyroscope　are　obtained.　The　accuracy　and　effectiveness　of　the　comprehensive　mathematical　model　are　validated　by　the　existing　models　in　literature.　The　necessity　of　taking　rotary　inertia　into　account　is　discussed.　The　natural　frequencies　of　the　rotating　piezoelectric　beam　in　both　drive　and　sense　directions　have　been　investigated　by　considering　the　effects　of　the　tip　mass,　angular　speed,　and　external　impedance.　The　dynamic　behaviors　of　the　piezoelectric　gyroscope　with　different　parameters,　such　as　the　tip　mass,　the　lengths　of　piezoelectric　materials　and　beam,　and　the　external　impedance,　have　been　studied.　In　particular,　the　optimal　combination　of　the　external　excitation　frequency　and　the　external　impedance　for　the　best　calibration　curve　of　the　piezoelectric　gyroscope　is　identified.　Finally,　the　dynamic　performance　of　the　piezoelectric　gyroscope　under　varying　boundary　conditions　has　been　investigated　for　the　potential　practical　applications.