Abstract: For the application demand of compact and miniaturized pulse source, the design technique of two-stage square pulse forming network(PFN) with mutual coupling inductors is developed. First, the decoupling conditions of this PFN are introduced. The corresponding output current expressions are derived using Laplace transform in the three commonly used network configurations. By using the Prony series expression of square pulse, the analytic expression is obtained by solving the nonlinear equations, and the parameters of each network element are worked out. The influence of the coupling inductors' coefficient in the circuit is studied. Then, the design method of two-stage PFN with mutual coupling inductors is proposed. The simulation results show that the output pulse with a certain width flat-top can be produced by using the designed PFN. With the ingenious design of mutual coupling inductors, the PFN producing square pulse can be conveniently realized.