An optical system of LED variable-focus imaging lamp, comprises a LED light source module, a light-collecting assembly, a shutter assembly and a zoom lens assembly, which are installed in sequence according to the direction of a light path. Geometry centers of the module and assemblies are collinear with a primary optic axis A. A focal point F1 of the light-collecting assembly coincides with a focal point F2 of the zoom lens assembly. The zoom lens assembly comprises a first zoom lens, a diaphragm and a second zoom lens. The first zoom lens and the second zoom lens can move forward or backward along the direction of the primary optic axis A so that zoom is realized. The diaphragm is disposed between the first zoom lens and the second zoom lens, and the clear aperture of which is adjustable.