Due to the complex matrix effects in bulk water, the application of laser induced breakdown spectroscopy (LIBS) in online continuous detection and analysis of liquid sample is limited. Thus, we propose a new method of LIBS assisted by micro hole spraying technology. The essence of this method is to transform the flowing liquid sample into dense droplets and spurt out continuously through a micron hole matrix and piezoelectric ceramic in order to assist the analysis of LIBS. A detection experimental system is established, composing of a micro hole ultrasonic system, a 1064 nm Nd∶YAG laser and a fiber optic spectrometer. A series of experiments and analysis are carried out to detect the calcium element dissolved in pure water with the detection experimental system. The optimum experimental parameters, the physical properties of plasma and the analysis ability of this method are studied. The results show that the limit of detection for calcium element is as low as 0.96 mg/L. And there is a good linearity between spectral peak intensity and concentration within the range of 0-1124 mg/L.