Multi-photon entangled states which are produced mainly by the process of spontaneous parametric down conversion between laser and second-order nonlinear material is a key resource in the quantum network. Although the application of pulsed laser improves the nonlinear conversion efficiency and simplifies the quantum communication protocol, it is still necessary to enhance the interaction between laser and material for improvement of multi-photon production rate. A resonant cavity for femtosecond pulse is designed to increase the parametric gain and multi-photon production rate while keeping its repetition rate and comb structure. The improved single- and two-photon production rate of cavity system are enhanced by 6.25 and 38.6 respectively compared with that of the single-pass system. The experimental results show agreement with theoretical predication.