Abstract: Glass curtain wall construction with single-layer cable net is widely adopted structural form in nowadays Chinese public great buildings. Because of its large deflection and high nonlinearity, the dynamic performance of cable net is greatly different from that of the conventional linear structures. The continuous membrane theory was used to formulate the nonlinear vibration differential equation of cable net, and harmonic balance method was used to solve the analytic formula of the nonlinear frequency. In order to verify the above analytic formula, its analytical results were compared with those of the precise nonlinear FEM time-history method. The comparison tells us that the two sorts of results have good accordance. It implies that the analytic formula has high precision. At the same time, it is pointed out that when the structural displacement is of the amplitude of vibration, the stiffness of cable net is the equivalent linearized stiffness based on the equivalent energy, and the above nonlinear frequency analytic formula can be obtained by equivalent linearized stiffness. Furthermore, the nonlinear vibration differential equation and nonlinear frequency gained by the study is the basement of the response analysis of cable net under dynamic load.