Fertilizer is the key factor for increasing rice yield, and solves accumulation blockage, difficulty in regulating fertilizer amount and poor uniformity of fertilization in the existing fertilization machinery, and a side deep fertilizing device which was easy to adjust the amount of fertilizer and prevent blockage was designed, referring to the agronomic requirements of side deep fertilization in paddy field and structure of transplanter, and the basic structural parameters of the device were determined. Through theoretical analysis, the working process of the device was explored, with simulation software, the effects of fertilizer discharge disc speed and fertilizer tank height on fertilizer filling and discharging were investigated, the optimum operating speed range of fertilizer discharge disc was 10~50r/min. Through bench test, the effects of fertilizer discharge disc speed and fertilizer tank height on fertilization stability and the effects of fertilizer discharge disc speed and transplanter speed on fertilization uniformity were obtained, the fertilization results met the national standards, and the fertilization uniformity was improved to a certain extent compared with the fertilization machinery on the market. With field test operation, the operation effect met the agronomic requirements. The research designed a kind of fertilizing device which was easy to regulate the fertilizer amount, antiblocking device with uniform fertilization, provided a reference for the operation of the side deep fertilizing device for paddy field.