In this paper, the negative hydrogen ion transportation and energy deposition mechanism are investigated deeply, and the collisions between negative hydrogen ions with other particles are treated by the three-dimensional Monte Carlo method. The storage of the particles and the constraint function of magnetic field are disposed by particle-in-cell (PIC) technology under the CHIPIC software. Based on this, negative hydrogen ion transportation and scattering case in the JAERI 10 A multicusp ion source are simulated. The influences of pressure and filter magnetic field on negative hydrogen ion transportation and extraction characteristics are analyzed and discussed. Results show that the greater the pressure, the bigger the collision loss of the volume produced negative hydrogen ions, and also the smaller the number of negative hydrogen ions reaching the wall and extracted is; in the lower discharge case, the more intensively the negative hydrogen ion extraction is influenced by the filter magnetic field, and also the stronger the filter magnetic field, the worse the extraction effectiveness is.