A dual-frequency slot patch antenna in the terahertz region is presented. Loaded with C-and E-type radiation slots on the patch,the current path on the patch surface was modified to realize the dual-band characteristic. The simulation based on HFSS 15.0 modeling shows that the antenna can simultaneously operate well at two bands,namely 300 GHz (291~306 GHz) and 640 GHz (632~656 GHz). The corresponding maximum gains are 7.38 dB and 10.50 dB,respectively. The dual-band antenna has the characteristics of simple structure and stable performance,and it has the application value for terahertz communications and wireless transmission systems.