Abstract: The cutoff frequency of single mode, dispersion and loss of a novel terahertz polyethylene photonic crystal fiber with triangle core were investigated by using the full-vector finite element method (FEM). The results show that the terahertz frequency range of the single-mode is tailored by the cladding pitch, cladding air hole and core air hole diameters. 0.1-5 THz broadband single-mode transmission is obtained and waveguide dispersion is limited in 0.5 ps/(nmkm) for wavelength of 60-450 m, and the transmission loss is 2.67 dB/m at 2.8 THz.