Model order reduction (MOR) is a new technique to generate a smaller system from a large input and output system.The reduced order technique is an e?ective approach to replacing a large system (normally,linear and very large) by a reduced system of lower order.An e?ective MOR method not only possesses good approximation precision but also preserves the essential properties of the original system,such as stability,passivity,controllability,and observability,and so on.In this talk,we will present some model order reduction methods for engineering systems,which includes asymptotic waveform evaluation (AWE),Krylov subspace techniques (Arnoldi,PRIMA,SPRIM),truncated balanced realization (BTR),and nonlinear model order reduction.It is really a potential and possible powful tool for simulating or designing complicated or large time-dependent systems.