Abstract: The combined spray gun is a high-efficiency, wide-coverage, long-range and mechanized spraying assembly unit. It was especially utilized for prevention and cure of sickness and grass/insect harm in the water-field. According to the particular requirement of water field routine missions that require the spray gun ought to fulfil the large flux, expanse-scope, long-range and a special trait of uniformity around the spray area. This academic research started from the analysis of primary principle then to study and test the speciality of the spraying to clearly identify the most optimized combination of long-range, conical and slit nozzles in order to realize: ① to maintain the effective spray range in 10m under the prescribed flux and working pressure; ② the uniformity of the liquor spraying in the spraying domination that the coefficient of variance less than 0.35. Also at the arrangement of multi-style nozzles, the innovation of multi-style spraying domination and spraying uniformity are achieved.