The spray coating process is an important process of the coating particle technology for the production of controlled-release fertilisers (CRFs). Its modelling would be helpful in the production process such as increase material usage efficiency, save production costs, and reduce dispersal waste produced that will cause environmental pollution. This article presents the results of an experimental study to establish an empirical model of the spray coating process with a biodegradable polymer solution. The shape and size of the spray area, droplet size distribution (DSD) and Sauter mean diameter (SMD) were determined by using high-speed camera 1000 frames per second (fps), laser transmitter and the image processing toolbox of MATLAB software. The results showed that the spray area had a cone shape, its mean width, corresponding to a spray distance of 300 mm, was 451 mm at a pressure of 0.18 MPa, viscosity of 50 mPa.s, spray flow of 1.5 mL/min and the droplet size distributions were noted 0.153 to 1.449 mm and droplet SMD was 0.876 mm. The model also showed that droplet SMD was calculated by four dimensionless numbers, will be applied to calculate, optimize and simulate coating particle technology.