With　the　construction　of　periodic　functions　relative　to　the　meshing　frequency,　rotating　frequency,　and　the　faulty　frequency,　etc.,　the　phenomenological　model　provides　a　simple　and　effective　way　of　representing　the　vibration　signal　of　the　planetary　gearbox.　However,　due　to　that　the　meshing　vibration　is　simplified,　the　traditional　model　can　only　reflect　the　modulation　characteristic　of　the　signal,　but　not　the　impact　characteristic.　Therefore,　an　improved　phenomenological　model　is　proposed,　which　can　satisfy　these　two　characteristics　of　the　vibration　signal　at　the　same　time.　To　consider　the　meshing　vibration　correctly,　two　key　points　should　be　determined:　occurring　moment　of　impact　signals,　and　their　relative　amplitudes.　In　order　to　calculate　the　occurring　time,　this　paper　proposes　modifying　the　reference　point　of　the　meshing　phase　and　using　the　modified　phases　to　represent　it.　Then　two　experiments　are　designed　to　verify　the　correctness　of　the　modified　phases　and　the　occurring　moment.　Fortunately,　these　experimental　results　also　provide　a　factual　basis　for　determining　the　relative　amplitudes　of　these　impact　signals.　Subsequently,　signal　model　of　the　gearbox　in　the　healthy　state　is　established　based　on　the　meshing　vibration　characteristics.　The　simulation　results　show　that　the　new　model　can　satisfy　the　modulation　and　impact　characteristics.　In　addition,　combined　with　the　time-varying　meshing　stiffness　of　the　gear　pair,　the　paper　theoretically　analyzes　the　influence　of　fault　type,　location,　and　size　on　the　impact　frequency　in　a　fault　meshing　period.　Finally,　the　correctness　of　the　new　phenomenological　model　is　verified　by　experiments.