A numerieal sim ulation is used to cakulate the near—field intensity by “split light beam ”. The preliminary resuRs of the calculation on one dimension compact disk sample using plane wave are demonstrated. It shows that the near—field intensity profiles have rather complicated structures. In many cases the near—field intensity does not represent the actual surface profile. The near—field intensity is strongly modulated by the surface structure. When the distance between the sample and the proble becomes larger, some subtle oerturhation is added to the intensity profile. and a shift be tween the surface profile and the intensity distribution be came more remarkable. The shift may cause some problems when we use the optical probe as a multi—function probe to do some lithograph work or to position. A comparsion be tween the calculation and other experimental results is also made.