Abstract: State synchronization is an important direction in the complex network field. However, the actual state of system is often unable to observe, and sometimes only part but not all of states is needed to make the synchronization to come true. Therefore, a new complex network model with output available is proposed as an extension of original complex network model. Then, according to the output matrix which is either singular or nonsingular, the stability of the output synchronization of complex network is analyzed and some sufficient conditions are given to it in form of lemma. Furthermore, the conditions for stability in case the output is synchronous but the state is asynchronous are studied, and an example is given to illustrate that the output synchronization is available even if the conditions for state synchronization is unsatisfied. The results reveal the significance of output synchronization in complex network systems.