Liquid-assisted laser machining (LALM) is a composite manufacturing technology. During liquid-assisted laser ma-chining, the liquid has the functions of cooling and cleaning on the processing area. It makes the heat affected area of the work piece become smaller. The thermal stress is reduced, and the processing incision is smooth and cleaning. So the liquid-assisted laser machining has unique advantages in the processing of heat sensitive materials, high hard-en-brittle materials and materials of high precision requirements. Due to the addition of liquid in the laser processing, the laser interacts with the machined and the added working liquid. Some researchers have found that the pressure in the process of liquid-assisted laser machining is produced through the study of the experiments and simulation. The existence of pressure results in the complexity of the laser processing even the processing mechanism would be changed. Then the process is difficult to be controlled. Therefore the process of liquid-assisted laser machining should be detected. In order to better master and control this technology, many researchers have studied the existence of pressure in the process. And it has become a research hotspot in the field of laser composite processing. At present, most of the numerical simulation and experimental studies on the pulsation, shock wave, micro-jets and acoustic radia-tion of single bubble generated by single pulse laser are carried out. However, multi-bubble is usually produced in the process of liquid-assisted laser machining, which makes the phenomenon and the mechanism of laser processing be-come more complex. These complex phenomenon and mechanisms should be further explored and studied by re-searchers.