Macroscopic and microscopic atomization characteristics of a gasoline injector operated at high pressure in a direct-injected gasoline engine are explored both experimentally and numerical. The spray development, macroscopic analysis, and spray characteristics are investigated under the conditions of various injection pressures and spray cone angles. The quantitative spray characteristics and spray developing processes are obtained by using a phase Doppler particle analyzer and a particle motion analysis system, respectively. The numerical study is conducted using KIVA-3 code for the same operating conditions as the experimental conditions. In order to improve the prediction accuracy, the code is modified to contain the Kelvin-Helmholtz (KH)lRayleigh-Taylor (RT) breakup model based on the competition between KH and RT instabilities. The results provide the influence of injection pressure and spray cone angle on the spray developing processes, spray tip penetration, and atomization characteristics such as mean droplet size and mean velocity of droplets. The predicted results of spray behavior and microscopic characteristics agree with the measured results of spray characteristics.