The coherent submillimeter wave generated from the GaAs surface exited by ultrashort optical pulses is incident- angle dependent and the ratio of forward and backward radiaion is related with the optical incident angle. The relationship between the thichness of the metal film coated on GaAs surface and the amplitute of submillimeter wave are measured. The theoretical model of the photon carrier dipole gives a well explanation on the angle dependent relatonship and the polarization of the coherent submillimeter wave.