A method to control the transmission characteristics of the THz wave in a silicon wafer by using a laser to irradiate the surface of a high resistance silicon (H--Si) wafer is presented. First, the laser at the wavelength of 808nm is used to irradiate the H--Si wafer so as to let it generate the photoinduced conductance. Then, the photoinduced conductance is used to control the absorption coefficient of the THz wave and hence to control the transmission characteristics of the THz wave in the silicon wafer. The transmission characteristics of the THz wave in the silicon wafer is measured when it is irradiated by the laser with a light intensity of 1.9W/cm2. Under the irradiation by the laser with a light intensity of 1.9W/cm2, the transmission of the THz wave in the 0.07cm silicon wafer is reduced by 20%. The experiment shows that it is feasible to control the transmission of the THz wave in a silicon wafer by using a laser.