Clamping tool for welding gas tank

The invention relates to a clamping tool for welding a gas tank. The clamping tool comprises a base, a left fixing piece, a right fixing piece and a shape fixing block, the left fixing piece and the right fixing piece are installed on the base and used for fixing two opposite side plates on the gas tank respectively, and the left fixing piece and the right fixing piece are arranged in a spaced mode, so that a containing interval used for containing the gas tank can be formed between the left fixing piece and the right fixing piece, the left fixing piece and the right fixing piece are each provided with a locking structure used for fixing the gas tank; the shape fixing block is installed on the base and provided with a supporting section, the front portion of the supporting section is small, the rear portion of the supporting section is large, and the supporting section is used for being inserted into a sleeve penetrating hole in a front cover plate of the gas tank from back to front and supporting a rear side