The invention provides a processing method for reducing the carburizing and quenching deformation of a helical gear. The method includes the following steps that a helix angle variable beta' for reverse deformation is reserved for helix gear machining before carburizing and quenching of the gear, that is to say, the machining helix angle of the helical gear before the carburizing and quenching process is equal to a value obtained by subtracting the helix angle margin beta' for revere deformation on the basis of a design helix angle beta; the helix angle variable beta' is set according to the design helix angle beta of the gear, the tooth-direction effective analysis range H of the gear and a tooth-direction heat treatment deformation amount M in the gear hobbing or gear shaping process. Inthe method, based on the reverse deformation rule, the distortion generated by heat treatment is offset by the helix angle variable. The helix angle meets process requirements after carburizing and quenching of the gear, it is guranateed that the upper and lower section deformation will not be out of tolerance after carburizing and quenching in subsequent finish machining of the tooth-direction gear, the workload of subsequent finish machining is reduced, and the cutting amount of a carburized layer is reduced.