Tooth　crack　is　a　non-negligible　issue　that　causes　the　vibration　response　of　a　gearbox.　Therefore,　the　operating　status　of　the　gearbox　is　always　detected　to　remove　the　presence　of　dangerous　situations.　Therefore,　the　effect　of　a　gear　tooth　crack　on　the　vibration　response　of　the　gearbox　is　important　for　the　gear　condition　monitoring.　The　accuracy　of　meshing　stiffness　analytical　model　is　the　basis　for　effective　dynamic　simulation;　for　this　account,　a　universal　equation　of　a　gear　profile　that　is　in　reference　to　the　actual　process　of　manufacturing　is　presented　to　improve　the　meshing　stiffness　model　for　a　cracked　tooth.　Based　on　the　actual　gear　profile,　in　theory,　two　affecting　lines,　the　parabolic-affecting　line　(PA)　and　the　straight-affecting　line　(SA),　are　introduced　to　study　the　effect　of　an　angle-changing　crack　on　the　gear　mesh　stiffness.　Afterward,　the　influence　of　the　angle-changing　crack　on　the　vibration　response　is　investigated　both　in　the　time　domain　and　in　the　frequency　domain.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.