Rice is the most important crop in China, which has the largest plant area. Fertilization is an important process of rice production, which directly affects the yield of crops, reasonable and effective use of chemical fertilizer can improve the yield of crops. At present, the mechanization level of rice fertilization is very low in China, and the artificial fertilization requires a large amount of fertilizer which caused the uneven distribution. The rice side deep fertilizing is an ideal way of fertilization, the fertilizing device will fertilizer (fertilizer for basal and tiller) based on the agronomic requirements one-time positioning and quantitative, it can apply a uniform fertilization to the rice side with a certain depth, which can reduce nitrogen fertilizer amount of 20%-30% compared with the traditional fertilizing operation. The study design a device of air-assisted side deep precision fertilization combined with the agronomic characteristics of side deep fertilization. This device adopted modularization design and riding type rice transplanter supporting the use. In the process of operation, the fertilizer granules falls into the deep trench at a certain amount under the effect of gravity and wind, the trench is drew by fertilizer exports in seedling side 3cm and 5cm depth, and then the fertilizers will be covered in the mud by covering plate. The vehicle control terminal is designed under the embedded Visual C++ integrated development environment in the XP Windows operating system, the interface can display the current operating data, and meanwhile, the user can set the working parameters according to the actual operating requirements. The experiments were done in the field of Heilongjiang seven star farm, the result shows, planting and fertilization can be done completely and independently in one time when fertilization device and riding type rice transplanter supporting the use. When the preset rate of fertilizer was 300 kg/hm2, the vehicle speed was 1m/s fertilization device can realize the precision fertilization, and the deviation of fertilizer is within 5.82%, which can meet the requirement of the actual production.