One-dimensional photonic crystals (PhC) based on silicon with infiltrated nematic liquid crystals (NLC) are investigated in this paper. We show that the band structure and photonic band gap can be continuously tuned by changing external voltage. The applied voltage variation will affect the direction of liquid crystal molecules, altering the refractive index near the waveguide. We considered arbitrary direction of propagation of electromagnetic waves. The band structure, group velocity and band gap can be tuned by changing applied voltage to modify the direction of LC molecules. We used the finite element method (FEM) to calculate the optical characteristic in anisotropic material system. A large tuning range of about 49 nm at a low operating voltage of 10 V is achieved due to the optical anisotropy of the NLC molecular.