The Si2+ + H collision ionization is studied using classical trajecto ry Mo nte-Carlo (CTMC) method. The total cross section as functions of the energy of i ncident projectile, single differential cross section and double differential cr oss section as a functions of the energy and the angle of the ejected electron a re calculated. The ionization mechanisms of soft collision, electron capture to the continuum state,binary encounter collision are demonstrated. The effect of “saddle point" is also discussed by calculating the ejected electron distributi on depending on the ratios of distances between electron and target and between electron and projectile.