The invention provides a lamp cap of a lamp. The lamp cap comprises a heat-conductive plastic part, a lamp holder, a cavity and a lamp cap pin, wherein the heat-conductive plastic part is integrally formed from heat-conductive plastic, and cooling fins are arranged around the heat-conductive plastic part. The lamp cap of the lamp has the advantages that the structure is simple, safe and reliable,a heat-dissipating structure is provided, the volume is small, the lamp cap can be replaced at any time, is suitable for occasions where the height of a lamp body is required, can be open mounted andcan also be used in combination with the lamp, a common GU10 lamp holder is used, the lamp can be provided with an LED driver, the lamp cap is concealed in the heat-conductive plastic part when beingmounted, the replacement is convenient, the volume is small, and the overall height of the whole lamp after installation is effectively reduced.