Aerosol sprays are used in many fields because they are easy to use and low in cost. Because flash-boiling has a great influence on atomization performance and spray characteristics such as droplet diameter and spray cone angle of aerosol spray, it is necessary to adjust the flash-boiling by changing the internal design of the aerosol vessel to obtain the desired atomization performance. Therefore, spray structure formed on the outside of nozzle during both transient and steady state. with various nozzle design and internal liquid/propellant composition ratio were observed in this study. The spray development process was visualized using a high-speed camera and Nd:Yag laser was used to form a laser sheet and it illuminates the internal structure of spray at steady state. In addition, the diameter and velocity of spray droplets were measured by PDPA equipment, which uses a noninvasive method. Selected design parameters were the number of stem orifice and the diameter of under-tap of the valve and vapor phase tap, and the mass fraction of propellant inside the aerosol vessel. As the diameter of the under tap increased, the ratio of the high-density area increased. However, as the difference between the area of the under-tap orifice and the total area of the stem orifice became smaller, the spray cross section area became larger and the shape of low-density region became closer to the concentric circle. In addition, finer droplets were generated in case with large stem orifice & smaller under-tap. The Vapor Phase Tap and propellant mass fraction have the greatest influence on the atomization characteristics of all design parameters because they change the gas phase ratio inside the jet. However, higher propellant mass fraction makes more uniform droplet diameter distribution than increased vapor phase tap diameter.