Abstract: Fertilizer is an important condition for the crops growth and yield. In recent years, the use of agricultural fertilizer in China has increased significantly, which has brought a lot of environmental pollution and resource waste. Therefore, rational fertilization is one of the urgent problems in agricultural production. In order to solve the problems of unreasonable fertilizer distribution and low efficiency in banana fertilization operations by hands, this paper designed a variable rate fertilizer applicator based on the distribution characteristics of the banana roots. The distribution characteristics of banana roots at different growth stages were analyzed statistically, and the theory of variable rate fertilization was constructed. The fertilization decisions based on the distribution characteristics of banana roots were obtained, and the variable rate fertilizer applicator was designed, the prototype experiments were carried out. The results showed that the length of fertilization at the banana seedling stage was not more than 22 cm, the amount of total fertilization was not more than 0.150 kg, the ratio of fertilizer amount sowed in the primary and secondary fertilization areas was about 5:8:5 and the fertilization length ratio was about 1:2:1. The fertilization length at the vegetative growth stage was not more that 42 cm, the amount of total fertilization was not more that 0.200 kg, the ratio of fertilizer amount sowed in the primary and secondary fertilization areas was about 1:2:1 and the fertilization length ratio was about 1:5:1. The length of fertilization at the reproductive developmental stage was not more that 84 cm, the amount of total fertilization was not more that 0.300 kg, the ratio of fertilizer amount sowed in the primary and secondary fertilization areas was about 5:11:5 and the fertilization length ratio was about 1:3:1. The field tests results showed that when the forward speed of the fertilizer applicator was 0.38 m/s, the rotation speed of the fertilizer plate was 22 r/min, and the central angle of the leaking hole was 120°, the average relative error between the theoretical value and the actual value of the fertilization amount was 5.74%, the qualified rate of fertilizer application was 93%, which meet the requirements of banana fertilization operation. The growth of banana plants fertilized by variable rate fertilizer applicator was better than that of the conventional artificial drill fertilization.