The direct injection into the cylinders has been regarded as a way of the reduction in fuel consumption and some pollutant emissions in gasoline engine. Its spray is of paramount importance in that the primary atomization process must meet the requirement of quick and complete evaporation and combustion. And the spray geometry must be stable and have robust against pressure change inside of the cylinder. The effect of injection signal, such as induced voltage and nozzle opening/closing time on the spray characteristics including spray geometry and atomization were investigated in a constant volume chamber by using gasoline direct injection piezo actuated outward-opening injector. The macroscopic, microscopic Mie scattering images were taken, Phase doppler anemometer technique was applied to measure droplet size. And injection rate was measured by Bosch method to evaluate the response characteristics of injection.