In aviation, the machine quality and accuracy of herringbone gear are strictly required, and its realization depends on the grinding process. There is an urgent need for further expansion of grinding wheel diameter. This paper proposed a gear gap space borrow grinding method and determined the analyzing relation between grinding wheel diameter and herringbone gear design parameters. Based on certain assumptions and idealized processing methods, the method of the gear undercut width design and the wheel maximum diameter determination are completed by geometry modeling combining the analytical and simulation method. After solid contact simulation verification, several important phenomena have been discussed, then valuable laws and conclusions have been obtained.