The　influences　of　Allee　effect　and　density-dependent　mortality　on　population　growth　are　of　great　significance　in　ecology.　In　this　paper,　we　first　consider　a　Gause-type　predator-prey　model　with　simplified　Holling　type　IV　functional　response,　strong　Allee　effect　on　prey,　and　density-dependent　mortality　of　predator.　It　is　shown　that　the　system　exhibits　rich　and　complex　dynamics　like　bistability,　local　and　global　bifurcations　such　as　transcritical　bifurcation,　saddle-node　bifurcation,　Hopf　bifurcation,　cusp　bifurcation,　Bogdanov-Takens　bifurcation,　Bautin　bifurcation,　homoclinic　bifurcation,　saddle-node　bifurcation　of　limit　cycle,　and　heteroclinic　bifurcation.　Next,　we　separately　explore　the　influences　of　Allee　effect　and　density-dependent　mortality　on　the　dynamics　of　the　same　model.　The　results　show　that　the　strong　Allee　effect　induces　the　occurrence　of　heteroclinic　bifurcation　and　the　reduction　of　the　number　of　limit　cycles,　while　the　density-dependent　mortality　stabilizes　the　system.　Since　the　analytical　expressions　of　the　interior　equilibria　are　difficult　to　derive,　the　results　are　verified　numerically.