A terahertz photoconductive antenna with adjustable polarization is proposed, which consists of four arc structure metal electrodes, a low-temperature gallium arsenide substrate and an anti-reflection layer of silicon nitride. Through the analysis of the working principles of photoconductive antenna, it can be found that the arc metal electrode structure determines the radiation polarization of the antenna, and the carrier mobility, carrier life and laser absorption of the substrate material can directly affect the radiation characteristics of the antenna. The photoconductive antenna is modeled and simulated by COMSOL software, and the results show that the antenna can multiply the outgoing polarized terahertz wave in the 45° direction, and the radiation intensity is 30% higher than that of the conventional photoconductive antenna and the radiation bandwidth is up to 10THz. The designed terahertz photoconductive antenna has the characteristics of adjustable polarization, simple structure and easy processing, owning broad application prospects in the field of terahertz spectrum detection.