Based on the plane wave approximate theory for terahertz generation via difference frequencies, the characteristics of terahertz wave generated in GaP pumped by dual- wavelength ceramic laser is investigated, including the phase matching, output power and temperature behavior. Results show that the coherent length is large enough via collinear matching method by use of the pumping light near 1060 nm. The output power of the terahertz emission relates to the crystal length and there is an optimal value for specific terahertz wavelength. The phase matching effect can be adjusted via changing the temperature of the GaP crystal, so different phase matching wavelength ranges can be obtained. The simulation result can provide some guidance for terahertz generation in GaP via difference frequency pumped by dual-wavelength ceramic laser.