Based on plane wave expansion method, complete photonic band gaps (PBGs) of a woodpile three-dimensional (3-D) terahertz (THz) photonic crystal (PC) with face-centered-tetragonal (fct) symmetry are optimized by varying structural parameters and the highest band gap ratio can reach 26.71%. In order to further optimize the complete PBGs, we propose a novel woodpile lattice with comparatively decreased symmetry and the highest band gap ratio can be increased to 27.61%. The woodpile THz PCs with two different symmetries both have a wide range of filling ratios to gain high quality complete PBGs, making the manufacturing process convenient. Woodpile 3-D PCs will be very promising materials for THz functional components.