The propagation and focusing of sound waves in liquid are simulated using finite element software. We find that delayed focusing can effectively reduce the echo time difference generated by different excitation sources. Additionally, the phase delay offset can effectively reduce the side-lobe amplitude of the focused beam. The increase in the laser excitation sources makes the beam directivity range narrowed to increase the energy amplitude at the focus; thereby, improving the imaging resolution and quality. Compared with a single laser source, the signal amplitude of eight laser source arrays can be improved by 3.46 times. Using post-processing focusing, multiple weak diffraction LIA signals are delayed and superimposed. The energy convergence is enhanced to realize higher precision detection at the target. The combination of the LIA-SAFT imaging method and PSM algorithm has good ability for acoustic beam synthesis, imaging resolution, and imaging quality. This study provides a new idea for LIA-SAFT imaging and shows a potential way of detecting underwater targets.