The present invention discloses a new and efficient heating tank for the fusion splicer and a fusion splicer, which comprises a heating tank body and a heating tank upper cover, among which, the said heating tank body is used to accommodate a heat shrinkable tube wrapped with a fiber welding point and heated to shrink the heat shrinkable tube, and the said heating tank body comprises a heating side surface and a heating bottom surface, while the said heating side surface and the heating bottom surface are connected with each other, and the heat shrinkable tube is in contact with at least either the heating side surface or the heating bottom surface during the preheating and thermal shrinkage; the said heating tank upper cover comprises a pressing portion, while the said pressing portion is narrower than the opening of the said heating tank body, and comes into contact with the heat shrinkage tube and exerts an acting force during the preheating and thermal shrinkage of the tube. The invention can speed up the thermal shrinkage process, reduce the heat shrinkage time, greatly improve the heat conduction efficiency, and reduce the cost, be more environment-friendly.