Combustion instability often occurs inside the combustion chamber of aero engine. Fuel atomization and evaporation, one of the controlling processes of combustion rate, is an important mechanism of the combustion instability. To tackle combustion instability, it challenges a deep understanding of the underlying mechanism of fuel atomization and evaporation. In this paper, acoustic field was established to simulate the pressure oscillation. Transient spray images of ethanol and kerosene were recorded using high-speed camera. The obtained images were processed by MATLAB to extract and analyze the related data. Spatial fuel atomization characteristics was analytically examined by multi-threshold image method to analyze the effect of the high frequency acoustic field on the fuel break-up and disintegration. The results show that the half spray cone angle on the side with speaker is suppressed by the presence of the imposed acoustic field compared with the case without speaker. Statistically, the half spray angle of kerosene with right speaker under the acoustic frequency of 9 kHz is 18.97% larger than that with left speaker. For ethanol, the difference is 11.90%. Also, it turns out the frequency of the acoustic field influences the spray angle variation during the injection process. There is a decline of the spray cone angle at the early stage of the injection. However, the watersheds for the transformation were not the same for kerosene and ethanol.