Abstract: We propose an approximate optimal fault estimation method based on complex network system estimator for a class of nonlinear systems with strong couplings. First, we jointly estimate the state and fault of the complex network via the augment method, and then perform the joint state estimation on the augmented state and fault. To address the data collision that may occur in multi-signal transmission, we transmit the output of the complex network to the remote estimator using an event-triggered approach. The parameters of the estimator are obtained by solving several recursive matrix equations such that an upper bound of the estimation error covariance is established and minimized. Finally, we present a simulation example to verify the feasibility of the proposed state estimation scheme.