The highest occupied molecular orbitle(HOMO) and lowest unoccupied molecular orbitle(LUMO) charge density distributions of adsorbed C60 with different orientations are calculated by using discreted variational-local density functional (DV-LDF) method. The theoretical simulations of scanning tunneling microscope (STM) images are based on Tersoff-Hamann theory. The results show that the charge density distribution parttens have their own‘fingerprint’. The LUMO charge distributions are more reliable than HOMO distributions when using them to simulate STM images. The molecular orientations can be easily determined by comparing with observed STM images in experiments and theoretical calculations in the literatures. Morevoer, according to the STM images obtained from our experiments, a new adsorbed orientation of C60 on Si(111)-7×7 surface has been found. Namely, C60 can adsorb with its 5—6 bond facing towards the substrate surface. At the same time, experimentalist can get some useful imformation from the results of this paper, and the orientations of the other molecules can also be determined by using the method.