Disclosed is a blood oxygenator. The blood oxygenator includes a blood inlet chamber, and a housing. A hollow cavity is arranged in the housing, and includes a heat exchange zone and a gas exchange zone. Multiple heat exchange filaments are arranged in the heat exchange zone. Multiple hollow fibrous membrane fibers are arranged in the gas exchange zone. The blood inlet chamber includes an inverted conical side wall and an end surface hermetically connected to an opening at one end of the inverted conical side wall, an opening at the other end of the inverted conical side wall is hermetically connected to one end of the housing, and the other end of the housing is hermetically connected with a cover body. The cover body is provided with a blood outlet, and the end surface is provided with a spiral liquid inlet pipe coaxial with the blood inlet chamber.