The invention discloses an automobile chassis speed reducer outer end cover and a thermal processing technology thereof. The automobile chassis speed reducer outer end cover comprises a body. The thermal processing technology comprises a thermal processing process. The body is of a disc structure. A circular groove is formed in the middle of the body. Four fixing through holes are evenly distributed in the outer circle of the body and include the first fixing through hole, the second fixing through hole, the third fixing through hole and the fourth fixing through hole. The thermal processing technology is characterized in that after austenitizing is achieved through heating, the automobile chassis speed reducer outer end cover is immersed into an appropriate quenching medium to be rapidly cooled. The automobile chassis speed reducer outer end cover has high enough tensile strength to resist stretching, tensile failure, thread slipping and abrasion, has high fatigue resistance and impact toughness, can resist fatigue and impact fracture and can be well applied to an automobile chassis.