Abstract: The motion characteristics of the spray droplet as the engineering background were investigated in this paper. The momentum equation of a single droplet in the air environment under room temperature and pressure was established to analyze the sedimentation characteristic, pursuit characteristic and motion trail. The calculation results show that under different initial conditions, there are two situations in which the gravity is greater than the drag force and the gravity is less than the drag force during the initial period of time. After the droplets leave the spray header, the vertical displacement increases rapidly. The larger the droplet size and the initial velocity are, the higher the vertical displacement growth rate is. The larger the difference between droplet size and initial velocity is, the shorter the chasing time and the smaller the chasing displacement will be. The closer the droplet size and initial velocity are, the longer the chasing time and the larger the chasing displacement will be. The larger droplet initial velocity, initial diameter and injection angle induce the slower the transverse velocity disappeared, the larger the lateral displacement reaches, and the larger the area covers by the spray droplet. The calculation results are helpful to optimize the design and layout of spray system in engineering practice.