An optical system for a stage lamp wherein the optical system comprises: a light source, a light condensing device, an effect component, a lens, a multi-reflector optical component fixed on an upper portion of the lens, a light emitted by the light source being reflected by the light condensing device and converged to form a main light beam along a transmission direction of the light, the main light beam sequentially passing through the effect component and the lens and being reflected by the multi-reflector optical component; wherein the multi-reflector optical component is provided with at least three reflective mirrors, and is connected to a at least three-stage linkage mechanism which is capable of driving the multi-reflector optical component, and achieving a three-dimensional dynamic light spot effect. When the optical system according to the present invention is applied to the stage lamp, one lamp simultaneously presenting a plurality of same dynamic spot effects is implemented.