The invention discloses a horizontal diesel tank bracket mounting structure for a diesel engine. The horizontal diesel tank bracket mounting structure comprises a shell. Four legs are arranged on thelower side of the shell to form a rectangle, the diesel engine is arranged inside the shell, a diesel tank bracket is arranged above the shell, a first groove is formed in the upper surface of the shell, a plurality of first cushion devices are arranged on the upper surface of the first groove, a first cushion plate is fixedly connected with the end, which is far away from the first groove, of each first cushion device, a plurality of insertion rods are arranged in the middle of the first cushion plate, each insertion rod is positioned between the two corresponding first cushion devices, penetrates the diesel tank bracket and the first cushion plate and extends to a position below the first cushion plate, and insertion rod grooves which are matched with the insertion rods are formed in theupper surfaces of the diesel tank bracket and the first cushion plate. The horizontal diesel tank bracket mounting structure has the advantages that the horizontal diesel tank bracket mounting structure is simple and is convenient to operate, mount and detach and good in cushion performance, and diesel leakage and risks of secondary accidents can be prevented.