In　this　paper,　we　consider　an　SI　epidemic　model　incorporating　additive　Allee　effect　and　time　delay.　The　primary　purpose　of　this　paper　is　to　study　the　dynamics　of　the　above　system.　Firstly,　for　the　model　without　time　delay,　we　demonstrate　the　existence　and　stability　of　equilibria　for　three　different　cases,　i.e.　with　weak　Allee　effect,　with　strong　Allee　effect,　and　in　the　critical　case.　We　also　investigate　the　existence　and　uniqueness　of　Hopf　bifurcation　and　limit　cycle.　Secondly,　for　the　model　with　time　delay,　the　stability　of　equilibria　and　the　existence　of　Hopf　bifurcation　are　discussed.　All　the　above　show　that　both　additive　Allee　effect　and　time　delay　have　vital　effects　on　the　prevalence　of　the　disease.