This paper introduces an approximate grinding method (AGM) and tooth flank deviation correction strategies for helical face gears (HFGs) generated by grinding worm, addressing the issue of singularities on the grinding worm thread surface that hinders HFGs grinding properly. Firstly, the tooth flanks of face gear and grinding worm are derived, and singularities on grinding worm are determined. Then, based on the grinding generation theory of HFGs, the AGM is proposed to solve the challenge of grinding HFGs with a large helix angle. Next, the tooth flank deviation of HFG generated by the grinding worm with the AGM is investigated, meanwhile, the tooth contact pattern and transmission error analysis are conducted. In addition, the correction methods of the HFG tooth flank deviation is researched. Finally, a grinding experiment is performed, and demonstrates the validity of the theoretical analysis of the AGM.