The characteristics of the gasoline jets from a single-hole direct injection injector were investigated by means of a long-distance microscope and a high-speed digital camera at various injection pressures and backpressures. The results showed that the surface waves were formed along the surface of the gasoline jets, and developed randomly with time. Discontinued surface waves usually broke up at the places where the direction of jet changed and formed dense small droplets. With the increase of injection pressure, the wavelength of the surface wave shortened and their frequencies rose, which promoted the breakup of jets. The distance between two adjacent radial branches of a jet decreased with increasing fuel injection pressure and backpressure.