Transmission characteristic of terahertz wave in two-dimensional regular triangular lattice metallic photonic crystal is analyzed and studied through frequency-domain finite element algorithm. Copper is chosen for dielectric cylinder, and the background material is air. By changing the incident direction of terahertz, lattice constant and the ratio of filling material, and combining with a thoroughly systematic analysis of the transmission properties of both the TM mode and TE mode, the transmission patterns of terahertz in metallic photonic crystal with regular triangular lattice are acquired.The research results indicate that the characteristics of transmission are related to the ratio of filling material, lattice constant and incident direction of terahertz, and the band gap ranges of TE mode and TM mode are also very different. These have provided theoretic foundation for the development and production of photonic crystal filter, reflector and E/H polarization in terahertz region.