Multi-nozzle spray painting procedure of the inorganic zinc shop primer was established in order to obtain uniform film thickness. The shop primer paint prevents the corrosion of steel block during shipbuilding. When the dry film thickness of shop primer is insufficient, rust will be generated on the steel block. Otherwise, thick coating of shop primer may be a problem of weld defect. So, it is important to obtain the uniform film thickness of shop primer. The uniformity of dry film thickness is affected by spray speed, distance from spray gun to target surface and overlapping span of spray path. In order to uniformly maintain coating thickness of shop primer, the coating procedure was established based on the correlation of shop primer spray variables.