Aiming at the pitch error of large cylindrical gear processed by using forming method,according to the evaluation method of pitch accuracy of large gear,the influences of thermal deformation error of machine tool,tool wear error and indexing error of rotary table on pitch error of gear were analyzed,and the influence laws of pitch indexing and continuous indexing on pitch error of gear were studied.Based on the cross tooth indexing,the gear finishing process was optimized to reduce the pitch error,and the optimization effect was verified by experiments.The results shows that by using the cross tooth indexing method,the thermal deformation,tool wear of the machine tool and the gear pitch error caused by the indexing resolution of rotary table can be effectively reduced,and the machining accuracy of large cylindrical gear pitch can be greatly improved.