To effectively measure the droplet size and distribution in multiphase flow, an ultrasound array scanning method based on extracting transmission attenuation information of multiphase flow is presented. In order to preliminarily prove the feasibility of the above method. A frequency domain numerical simulation with a pair of probes is established. The excitation/reception mode of the probe is: in each round of excitation, each element of the transmitter is successively excited from top to bottom. All elements of the receiver simultaneously receive the sound pressure that after interacting with fluid. The influence of size and distribution of oil bubbles on the absolute acoustic pressure data at the receiving probe is analyzed. It shows that with the increasing of oil bubble diameter or spacing, its influence of absolute sound pressure data increases slowly at first and then decreases slowly. The phenomenon of diffraction, scattering and transmission when ultrasound interacted with the oil bubbles is accurately reflected. It’s preliminarily proved that the above method could be applied to the testing of oil-water two-phase dispersed flow. The response form of the receiving probe to oil bubbles does not conform to the superposition theorem. The testing range, resolution and extreme of the method to oil bubble size and distribution are deduced under the above method and mode. It provides a theoretical foundation for accurately extracting the original data of ultrasonic tomography, thus realize the visualization and quantitative measurement of the size and position distribution of droplet information.