The observer synthesis of nonlinear large-scale systems is discussed. The nonlinearities satisfy the Lipschitz conditions instead of any matching conditions and exist on the interconnection terms and local system matrices. With the aid of the solution of the Riccati-type equation, the relationship between the nonlinearity bounds and the observer gains is derived. Moreover, the existence condition and seeking algorithm for the solution of the Riccati equation are investigated. An example with simulations is given to illustrate the application of our results.