The invention discloses a welding method and a welding joint for a butt weld of a cast steel pipe and a hot rolled steel pipe. The welding joint comprises a welding joint portion formed by weld ends of the hot rolled steel pipe and the cast steel pipe, the welding joint portion comprises two grooves and a base plate, the two grooves are formed in the weld ends of the hot rolled steel pipe and the cast steel pipe, the base plate extends from the weld end of the cast steel pope to the inner periphery of the hot rolled steel pipe, the distance from the top of the base plate to the outer periphery of the cast steel pipe is equal to the wall thickness of the hot rolled steel pipe, and the bottom of the base plate and the inner periphery of the cast steel pipe are in slope transition. The welding method includes the steps of integral casting of the steel pipes, machining of the grooves and the base plate, butt welding for connection and the like. The welding method and the welding joint have the advantages that welding difficulty can be lowered, stress concentration and residual stress generated in welding can be weakened, fatigue performance under reciprocate load effect is effectively improved, surplus height of the butt weld is reduced, and a welded product can acquire better appearance effects.