Although it is the main machine in rice fertilizer with large width and high efficiency, centrifugal disc type fertilizer spreader is still with the problem of poor uniformity of fertilizer and difficult to realize the control of variable rate fertilization in width direction. In order to adapt to the development of precise agriculture and meet the requirements of rice variable fertilization at the same time, which could make fertilizer reduced and yields for rice increased, a kind of variable pneumatic fertilizer applicator was designed. The machinery not only met the requirements of width, but also achieved the variable rate fertilization in width direction. The fertilizer spraying device which designed for the machine of fertilizer was analyzed theoretically, and a simulation analysis of air flow field was also made for the spraying device with different baffle structures. What’s more, relevant tests of fertilization uniformity were made for fertilizing amount of each row of fertilizer and fertilizer spraying device of different baffle types within their respective scope of fertilization at different rotational speeds. The results showed that revolving speed had no significant effect on fertilizing amount of each row of fertilizer, and fertilizing amount error of each row of fertilizer was within 5% of the average. However, revolving speed and baffle types of fertilizer spraying device had significant effect on fertilization uniformity within the scope of single spraying device, taking the fertilization variation coefficient as index, the whole fertilizer ejecting uniformity variation coefficient was superior to the other speed when the wheel speed was around 30r/min; on the other hand, the fertilization uniformity variation coefficient of the cone baffle spraying device was superior to the other spraying device whatever the wheel speed was, and when the wheel speed was more than 30r/min, the fertilization uniformity variation coefficient of this spraying device was less than 8%. In addition, some comparison was made on the influence of different baffle structure on air flow field and fertilization uniformity, some similarities of them were found, but the conclusion whether the air flow field had significant effect on fertilization uniformity cannot be made. Above all, in order to make the single spraying device have the better fertilization uniformity in the process of actual operation, the cone baffle spraying device can be used, on the premise of knowing the weight of target area for fertilization, adjusting the speed of the machine to make the rotated speed of the wheel achieve 30r/min or more, on this account, good fertilization uniformity can be obtained in this area.