Abstract: In this paper,the two-dimensional axisymmetric fluid model of pulsed discharge in water is established based on COMSOL. The convection and diffusion equations of carriers are solved by numerical simulation,and the electron density of plasma produced by discharge in water at nanosecond pulsed voltage is calculated. In order to study the effects of different discharge conditions on the discharge process,the changes of plasma electron density with the changes of pulse voltage amplitude,pulse voltage rising edge and electrode gap distance are analyzed in this paper. The simulation results show that with the increase of pulse voltage amplitude,the electron density of pulsed discharge plasma in water increases,and the peak time is faster,the rising edge of pulse voltage is shorter,resulting in the acceleration of positive ion streamer development,and the longer discharge gap in a certain range,higher plasma electron density will be obtained.