In the solid-state cathodoluminescence (SSCL), the spectrum is characterized by the appearance of short wavelength emission (405nm). By comparing the short wavelength and long wavelength emission (580nm) peaks at varies electric fields, it can be concluded that the exciton dissociation is the reason for the systematic variation of the spectrum. In this work, the exciton dissociation is investigated by using the combination of experimental and theoretical method. The following results can be obtained: the theoretical model is reasonable, and can account for the observations; the electric field is the main factor of exciton dissociation under lower electric field, with increasing electric field, both electric field and direct impact can result in exciton dissociation.