Aiming to generate the initial fields for the control forecast of the GRAPES global ensemble prediction system, based on the Global/Regional Assimilation and Prediction System (GRAPES) global model, the initial field generation scheme is studied, and a dynamical upscaling technique of the high resolution initial field is developed, and the feasibility of different schemes is verified. By comparing the spatial patterns of the initial fields obtained through different schemes, it is verified that the horizontal interpolation scheme has certain shortcomings, and the threedimensional interpolation for the Exner pressure variable based on the hydrostatic equation is of great importance. The results show that with the dynamical upscaling technique, the initial geopotential height and temperature noise problems due to the horizontal interpolation scheme can be improved by adjusting the global temperature and pressure fields, so that they are balanced according to the hydrostatic balance relation, and the initial field of low resolution obtained with the dynamical upscaling technique is suitable for the control forecast of the operational GRAPES global ensemble prediction system.