Optical rectification is one of the important techniques for efficient generation of terahertz pulses. The theoretical model of the optical-to-terahertz conversion efficiency in optical rectification by tilted-pulse-front pumping was built. On the basis, the influence of the different tilted angles from tilted-pulse-front pumping on the conversion efficiency was compared. The effect of the important factors on the optical-terahertz conversion efficiency was analyzed quantitatively, and the influence of the parameters of both the crystals and the femtosecond pulses on the conversion efficiency was discussed. The results show that the influence of the titled angle on the optical-terahertz conversion efficiency was very obvious. The optical-terahertz conversion efficiency increases first and then decreases with the increasing of the pulse duration, where as it increases with the intensity pump pulses. In addition, the optical-terahertz conversion efficiency decreases rapidly with the increasing of the absorption, while increases and then remains unchanged with the increasing thickness of the crystal. Hence it is not only necessary to take measures to meet phase-matching condition as far as possible and decrease the terahertz absorption in the crystal, but also choose optimal parameters of the femtosecond pulse and the nonlinear crystal.