The invention discloses a gear involute internal spline machining method and a gear. The gear involute internal spline machining method comprises the following steps: S1, punching an internal hole in the gear through finish turning; S2, machining an internal spline in the internal hole for the first time; S3, coating the surface with the internal spline with a layer of anti-seepage paint; S4, mounting the gear on a special tooling and subjecting the gear to carburizing treatment; S5, dismounting the gear from the special tooling and subjecting the internal spline to secondary finish machining in the internal hole; and S6, mounting the gear on the special tooling again and subjecting the gear to quenching treatment. According to the gear involute internal spline machined by utilizing the above technological process, the carburizing treatment process and the quenching treatment process are performed separately; before the carburizing treatment process, the surface of the internal spline of the gear is coated with the anti-seepage material, thereby reducing the tooth surface hardness of the internal spline and guaranteeing the secondary finish machining of the internal spline; and by adoption of the special tooling, non-uniform shrinkage during heat treatment is avoided and the machining precision is improved.