The present application discloses a battery casing and a lithium battery. The battery casing comprises a casing, a housing bottom, and a housing cover, wherein the housing is a cylindrical structure which has openings at two ends, the housing is formed by bending and welding plates, the plates are provided with first side edges and second side edges which are welded and connected, and the first side edges and second side edges are provided with a positioning structure. The housing bottom is welded to a first end of the housing, and the housing bottom is configured to seal the first end of the housing. The housing cover is welded to a second end of the housing, and the housing cover is configured to seal the second end of the housing distant from the housing bottom.