Abstract: Two-step method was adopted to grow InP on GaAs（100） substrates by metalorganic chemical vapor deposition（MOCVD）,morphology of low-temperature buffer（LTB） layers and epilayers were analyzed by atomic force microscopy（AFM）.The morphology of epitaxial layers inherites that of LTB layers,heat-treatment processes make buffer layers rougher,their root-mean-square（RMS） has the smallest value when LTB growth temperature is 450℃,it is consistent with the result of X-ray diffraction measurements.Compared with LTB layers,two dimensional（2D） growth is successfully realized in epilayers.