The invention relates to welding technology of a brass inner sleeve of a hot galvanizing crust of an explosion-proof fan. In the technology, an arc-shaped fixture is adopted to expand the brass inner sleeve with an opening on the inner wall of the fan crust to enable the outer wall of the brass inner sleeve to contact the inner wall of the fan crust without gap, upper joint lines and lower joint lines formed outside the upper and lower openings of the brass inner sleeve and on the inner wall of the fan crust are subjected to synchronous and continuous argon arc welding in turn and in the samedirection, after welding one section, the arc-shaped fixture is displaced in turn to carry out welding of the next welding workshop section, to finish welding of multiple workshop sections in a peripheral direction, the opening of the brass inner sleeve is reinforced, welded and leveled up and a layer of welding belt is reinforced on the welding workshop section. The technology ensures the brass inner sleeve and the inner wall of the fan crust to be welded without gap, ensures firm welding, enables the welding stress to be minimized, improves the welding strength and ensures the fan to have good quality and long service life and to be further fit for the use requirements of explosion prevention and seawater corrosion prevention, and the use requirements in other severe environments of easy corrosion.