The invention discloses a novel split type water tank of a diesel. The novel split type water tank of the diesel comprises an upper shell, wherein an upper opening is formed in the upper shell; a filter screen is arranged in the upper opening; a threaded hole is formed in the upper opening; a mounting lug is arranged on the upper shell; a lug screw hole is formed in the mounting lug; a buoy hole is formed in the upper shell; upper connecting sides are arranged on the periphery of the upper shell; a groove is formed in each upper connecting side; a positioning hole is also formed in each upper connecting side; a lower shell is arranged at the bottom of the upper shell; lower connecting sides are arranged on the lower shell; a positioning hole is formed in each lower connecting side; a lug is arranged on each lower connecting side; a fixing surface is arranged on the lower shell; a mounting lug is arranged on the fixing surface; baffles are arranged on two sides of the fixing surface; and a baffle screw hole is formed in each baffle. The grooves of the upper connecting sides are connected with the lugs of the lower connecting sides in an inlaid manner, the sealing effect of the upper shell and the lower shell is improved, and meanwhile, a gasket is arranged in each groove, so that air impermeability of combination is guaranteed; and the problem that the upper shell of the water tank and the lower shell of the water tank cannot be connected closely in the prior art is solved.