Abstract: Measurement result of droplet size is affected by many factors such as spray liquid property, flow rate, spray pressure, orifice shape, and so on. Droplet size measurement results are different under different test methods. That means the droplet size measurement results of nozzles under different conditions have no significance of comparison and direct utilization. Nozzle classification based on droplet spectrum ignores the difference of laboratory data and obtain the same or similar nozzle classification results. However, nozzle classification method and test criteria have not been popularized or implemented in China, which leads to a fact that the nozzles made in China can not be classified or be compared with international nozzles. If ASAE nozzle classification reference map is used directly, the classification result will be misjudged. In order to solve the problem of the lack of data and methods of droplet size classification for domestic agricultural nozzles, a standard test method for droplet size was established in NJS-01 plant protection low speed wind tunnel based on ASAE S572.1 standard. Test conditions were as follows: airflow speed was 6.7 m/s and sampling distance was 30.5 cm. Sampling area was the whole spray section of laser scanning at a certain sampling distance. After determined standard test conditions and procedures, five reference nozzles were tested, namely Teejet 11001, 11003, 11006, 8008 and 6510 stainless steel core fans nozzle. On this basis, a reference map for droplet size classification of reference nozzles was established, and a nozzle classification method based on the reference map was proposed. According to the reference map of droplet size classification in NJS laboratory, droplet size was divided into 6 grades: very fine (VF), fine (F), medium (M), coarse (C), very coarse (VC) and extremely coarse (XC). Due to the limitation of measurement range and accuracy of DP-02 laser particle size analyzer, in this paper, we only considered the droplet size classification of common plant protection nozzles, and did not measure IP-16 and 6515 reference nozzles, which correspond for categories of extremely fine/very fine (XF/VF) and extremely coarse/ultra-coarse (XC/UC). Droplet sizes of 24 to be classified nozzles were measured at the pressure of 0.2, 0.3 and 0.4 MPa. To be classified nozzles were Teejet F110 (01-08), Lurmark F110 (015-05), Lanao F110 (015-05), YZS80 (02-04) and YZK80 (02-04). Nozzles were classified according to the position of droplet spectrum polyline on the reference map. Compared with test classification levels of Teejet F110 (01-08) and Lurmark F110 (015-05) standard fan-shaped spray nozzles and nominal nozzle levels provided by manufacturers, our results showed that most of the test levels of nozzles were in accordance with the nominal nozzle levels provided by manufacturers, except for the inconsistencies of classification levels of individual nozzles under individual pressures, which could indicate that the reference map of droplet size classification established by NJS wind tunnel laboratory and the nozzle classification method based on droplet spectrum were correct and adaptable. Droplet sizes of Lanao F110, YZS80 and YZK80 nozzles under different pressures were classified by this classification method, and the classification level of nozzles increased with the increase of nozzle type (nozzle aperture), and decreased with the increase of spray pressure. The same type of nozzles can be classified into different levels under different spray pressures. Droplet size was influenced by geometry shape of nozzle, the order of droplet size from large to small was YZS80, F110 and YZK80 under the same nozzle number and pressure. The results of classification were instructive for perfecting technical parameters of domestic nozzles, making it easy for users to choose nozzle type and to determine working pressure.