Optical fibers play an important role in terahertz (THz) wave transmission systems, however, there is a lack of transparent materials used to fabricate THz fibers, which limits the transmission distance of THz fibers. To further improve the transmission characteristics of THz fiber, a high birefringence hollow core antiresonant fiber is designed. The fiber cladding consists of a circular dielectric tube and a rectangular dielectric layer. The fiber structure is asymmetric. The finite element method is used to analyze the influence of fiber structure parameters on its loss and birefringence characteristics. At 0.475 THz, the results show that the birefringence can reach 3.75×10-4, and the loss of x and y polarization modes are 0.077 dB/m and 0.395 dB/m, respectively. When the x polarization mode loss is ensured less than 0.1 dB/m, the high birefringence characteristics of THz fiber are achieved.