An automatic installation lamp, comprising: a shell body; and at least one automatic installation mechanism; wherein said automatic installation mechanism comprises: an elastic element; a fixing base; a support element having one end rotatably connected with a side face of said fixing base, wherein said elastic element is arranged between said support element and said fixing base to connect said support element and said fixing base respectively, wherein a free end of said support element is adapted to rotate towards a lower portion of the fixing base; a fixing element having a first catch element; and a limiting element having a triggering element and a second catch element, wherein said triggering element is activated to move away from the fixing base, and said fixing element is arranged on said support element, and said limiting element is movably or rotatably arranged on the side face of said fixing base, and said fixing element is arranged on an upper portion of said fixing base, and said limiting element is movably or rotatably arranged on said support element, wherein the free end of said support element is able to overcome a torsion provided by said elastic element, so that the free end of said support element rotates towards the upper portion of said fixing base as well as that said second catch element is hooked on said first catch element, and while said triggering element is activated to support said limiting element being moved down or rotated along said support element, said second catch element is detached from the first catch element, said limiting element is slidably or rotatably arranged on the side face of said fixing base, characterized in that said automatic installation mechanism further comprises an elastic resetting element erectly arranged between said limiting element and said fixing base, and said elastic resetting element is biased against said limiting element and said fixing base, wherein said elastic resetting element can be a group of springs, wherein said elastic resetting elements is erectly arranged between a bottom end of said limiting element and said fixing base, and is biased against a lower end of said limiting element and said fixing base. a shell body; and at least one automatic installation mechanism; wherein said automatic installation mechanism comprises: an elastic element; a fixing base; a support element having one end rotatably connected with a side face of said fixing base, wherein said elastic element is arranged between said support element and said fixing base to connect said support element and said fixing base respectively, wherein a free end of said support element is adapted to rotate towards a lower portion of the fixing base; a fixing element having a first catch element; and a limiting element having a triggering element and a second catch element, an elastic element; a fixing base; a support element having one end rotatably connected with a side face of said fixing base, wherein said elastic element is arranged between said support element and said fixing base to connect said support element and said fixing base respectively, wherein a free end of said support element is adapted to rotate towards a lower portion of the fixing base; a fixing element having a first catch element; and a limiting element having a triggering element and a second catch element, wherein said triggering element is activated to move away from the fixing base, and said fixing element is arranged on said support element, and said limiting element is movably or rotatably arranged on the side face of said fixing base, and said fixing element is arranged on an upper portion of said fixing base, and said limiting element is movably or rotatably arranged on said support element, wherein the free end of said support element is able to overcome a torsion provided by said elastic element, so that the free end of said support element rotates towards the upper portion of said fixing base as well as that said second catch element is hooked on said first catch element, and while said triggering element is activated to support said limiting element being moved down or rotated along said support element, said second catch element is detached from the first catch element, said limiting element is slidably or rotatably arranged on the side face of said fixing base, characterized in that said automatic installation mechanism further comprises an elastic resetting element erectly arranged between said limiting element and said fixing base, and said elastic resetting element is biased against said limiting element and said fixing base, wherein said elastic resetting element can be a group of springs, wherein said elastic resetting elements is erectly arranged between a bottom end of said limiting element and said fixing base, and is biased against a lower end of said limiting element and said fixing base.