An internal radiotherapy particle implantation device for implanting radioactive particles into cancer patients. The said gun body consists of a particle holder, a front and rear cover plate, an implantation needle buckle plate and a pusher catheter; the said implantation needle is perforated in the middle and the hole at the end is tapered to fit with the pusher catheter; the said particle holder includes a housing, a spring and a top rod inside the housing, and a particle storage clip screwed to the housing, where the top rod can be topped to the bottom of the slot along the storage slot of the particle storage clip under the action of the spring. The top rod can be topped along the storage slot of the particle holder to the bottom of the slot, and a through-hole is opened above the near bottom of the slot of the particle holder. The invention has a simple structure, easy to use features, can be continuously loaded with particles at a time, to the human body implantation can also be continuously launched, and easy to replace the particle bin, a procedure can be implanted to the patient hundreds of radioactive particles.