Spray characteristics play a key role in affecting combustion performance of piston aero engines. In this study, spray characteristics of two types of fuel, kerosene and gasoline, were investigated with an air-assisted fuel injection (A2FI) system under different working parameters, which included air and fuel injection duration, fuel-air interval, ambient pressure, fuel pressure and fuel temperature. The macroscopic spray characteristics were observed by high speed imaging technique. The main difference is that the elevated ambient pressure or depressed fuel pressure reduces the spray angle of kerosene while the gasoline's spray angle is basically constant. It is attributed to the joint effects of air disturbance and compressed air expansion. Phase doppler particle analyzer (PDPA) was utilized to study the microcosmic spray characteristics. It indicates that the droplet size is significantly influenced by air and fuel injection duration, ambient and fuel pressure and fuel temperature. The droplet velocity increases when ambient pressure decreases or fuel pressure rises, which can explain the performance of macroscopic spray characteristics accordingly. There exist evident differences as well as similarities on spray characteristics between kerosene and gasoline with A2FI system. The study is beneficial for combustion chamber optimization and fuel matching.