Abstract: A gear meshing mechanical model was established on the basis of Hertz contact theory. The change law of roll distance and angle was derived according to the involute forming principle. Making Newton cooling theory and Fou- rier law as its theoretical foundation,the convective heat transfer and friction heat flow of gear system were calculated combined with the shearer ranging arm working characteristics. It is the first time that the convective heat transfer coef- ficient was confirmed by comprehensively considering the heat transfer characteristics of gear and lubricating oil,lubri- cating oil and box inner wall,box external wall and external air. Making Blok theory as a foundation,the bulk tempera- ture was chosen as an initial temperature. The change law of gear surface flash temperature and contact temperature with the roll distance or angle was analyzed. The shearer ranging arm gear transmission system model was established by using Romax Design. Idle shaft gear pair solid-heat coupled characteristics was analyzed. Involute tooth profile mod- ification and its influence on temperature field was analyzed on the basis of Romax micro-geometric modification theory. The results show that the Hertz contact stress transient increased phenomenon is eliminated and the maximum con- tact stress reduces 72 MPa by the tooth profile modification. The tooth temperature distribution is improved by the high temperature zone moving from tooth root and addendum to tooth profile central after the modification and the maximum temperature decreases 31. 4 ℃ . The results provide a theoretical foundation for analyzing the shearer ranging arm gear transmission system tooth profile modification and optimization.