To improve the fuel consumption and exhaust emission for gasoline engines, Gasoline Direct Injection (GDI) system was spotlighted to solve above requirements. Thus, many researchers have been studied to investigate the spray characteristics and the fuel formation of GDI injector. In this study, we tried to study the characteristics of a direct injection gasoline spray by using entropy analysis and PIV methods. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. The PIV method was adopted to determine the fluid dynamics information at the spray. Also fuel formation within the cylinder in the case of early injection timing greatly influences combustion characteristics. This study developed the analyzing system for the mixing fuel with air using the Mie scattering method to visualize the fuel distribution. This technique was applied to a visualization single cylinder engine in order to investigate the spray behavior and fuel distribution. (C) 2004 Elsevier Ltd. All rights reserved.