The invention discloses a large mud pump shell adopting a wear resisting cast iron insert and a welding fixing method, and relates to a large mud pump shell and a welding fixing method thereof, in particular to welding fixing of a wear resisting insert combination lining of a large wear resisting mud pump shell. The large mud pump shell adopting the wear resisting cast iron insert consists of a pressure bearing shell and a wear resisting liner; the wear resisting liner is arranged on the inner wall of the pressure bearing shell; and the wear resisting liner includes filling layers, U-shaped insert spliced blocks, annular insert spliced blocks, locking blocks, shunt blocks, a clamping embedded part, a welding embedded part and a sealing plate. Multiple U-shaped insert spliced blocks with U-shaped cross sections are bonded on the inner wall of the pressure bearing shell; the filling layers are arranged between the U-shaped insert spliced blocks and the pressure bearing shell; the locking blocks with U-shaped cross sections are arranged among the U-shaped insert spliced blocks as needed; the annular insert spliced blocks with annular cross sections and tightly bonded with the U-shaped insert spliced blocks are arranged in an outlet of the pressure bearing shell; and the shunt blocks for shunting liquid are arranged near the wear resisting liner between the annular insert spliced blocks and the U-shaped insert spliced blocks.