Abstract: This article comprehensively analyzes the coarse microstructure in 20CrMoH steel gears after carburizing,quenching, and tempering, improvement measures have been proposed from multiple aspects, including preventing severe segregation of raw material components, coarsening austenite grains, controlling gear forging temperature,and optimizing carburizing and quenching processes. By controlling the strip segregation of raw materials within 2.5levels, austenite grain size above 5 levels, forging temperature between 950～1080℃, adding isothermal normalizing process, and carburizing below 920℃, the coarse structure of gears after carburizing, quenching, and tempering is effectively eliminated.