Physical systems such as, electrical power system, aircraft, chemical plants, urban traffic networks, digital communication networks, economic systems and control system can be described mathematically, which is complex and large in dimension. In most of the practical situations higher order model is obtained from theoretical considerations. The higher order model possess so many problems in the analysis and design. So, it is usually recommended to reduce the order of the model retaining the dominant behaviour of the original system. Order reduction techniques help to decrease the computational complexity, reduce the hardware complexity and better understand the large scale system. In this paper, an order reduction technique such as pade approximation and mixed method of routh approximation is used. In mixed technique, the routh approximation method is used for determining the denominator coefficients of the reduced model and the numerator coefficients are calculated by the pade method. The response of reduced order model obtained is compared on the basis of unit step response also time domain and frequency domain characteristics is calculated and compared with previously obtain model.