An embedded sliding assembly and positioning structure of a lamp reflector which allows a reflector to be assembled fixedly onto a lamp. The embedded sliding assembly and positioning structure have a positioning framework having a reflector assembly side, an end side and two lateral sides. A through-hole is formed at the center of the positioning framework, and the positioning framework is also provided with an assembly and positioning portion for assembly onto the lamp. An embedded sliding guide is set at an inner edge of the end side and two lateral sides of the positioning framework. The embedded sliding guide is set in a manner to guide the sliding and locking of the flange of the reflector. A positioner enables tight locking of the flange of the reflector to the embedded sliding guide.