Quantum entanglement is of great importance for quantum information, quantum computing, and quantum metrology. In this paper, a scheme for generating quadripartite entanglement is proposed by combining three four-wave mixing (FWM) processes. The effect of intensity gain of three FWM processes on quadripartite entanglement is studied by applying the positivity under partial transposition (PPT) criterion. We find that the quadripartite entanglement exists in this system, and the quadripartite entanglement is enhanced by increasing the gain of three FWM processes. Furthermore, the eigenvalues and eigenmodes of this system is investigated, and the results show that this system is composed of four independent squeezedmodes. Our theoretical results will provide a feasible scheme and theoretical support for the experimental generation of quadripartite entanglement.