Abstract: To check the corona onset field intensity on the surface of fittings inside valve hall, by taking a ±800 kV UHV converter station as an example, a 3D whole model is built for the valve hall with the external software and inputted into ANSYS for pre-processing. The electric field distribution in the high voltage valve hall under various working conditions within a cycle is obtained by the electrostatic field instantaneous load method according to the voltage waveforms simulated by PSCAD software. Accurate calculation of the electric field in some concerned areas is realized by using the sub-model method. The corona discharge on the surface of tubular fittings and spherical fittings is also checked throuth comparing the calculation results with the empirical equation and experimental data. In the checking process, the fittings with irregular shapes are processed equivalently. The checking results indicate that the fittings selected for the valve hall have a certain margin in corona control, which can meet the safety requirement. The research result can provide a good reference for designing fittings inside UHVDC valve hall.