The characteristic analysis of a class of nonlinear circuit and the synchronization transmission mechanism of the signal are researched, and the results are in agreement with the experimental phenomena. Firstly, the dynamical characteristics of the nonlinear circuit are analyzed. And then, based on the experimental parameters of synchronization transmission signals from two nonlinear circuits, the principle of synchronization transmission signal from nonlinear circuits is analyzed theoretically. Finally, using Hurwitz stability theorem, the value range of coupling coefficients is calculated when two nonlinear circuits transmit signals synchronously, and the results are in agreement with the experimental results.