Starting from the basic equation of off-axial reference beam holograms, this paper describes the interference type computer-generated holograms and discusses their features in terms of both wide and narrow fringes and gives the test results. Besides, the authors pointed out the reasonable range of the approximate calculation of the wave aberration and gave three sets of practical test results. It has been shown experimentally that the interferogram of the wavefronts of (-1, 0) orders is the same as that of (0, +1). The explanation for it is given as well.