For decreasing the high grating inscription scattering of previous array-hole microstructured Optical Fiber Grating (MOFG), a large circular side-hole microstructured optical fiber grating configuration is proposed and analyzed. In this new configuration, a section of array holes is replaced by one large circular hole that is filled with fluid of proper fluidic index. Simulation shows that, due to immunity of array hole and microlens effect, the grating inscription efficiency of this proposed structure is respectively 288% and 206% times of the conventional array hole microstructured optical fiber grating and Single Model Fiber Grating (SMFG), which shows its potential value in high efficient grating. Moreover, a symmetrical angle inscription method is also proposed to guarantee the symmetry of grating inscription field, which will contribute to improving the flatness of beam energy distribution and the corresponding birefringence in single angle inscription process.