The next generation wireless communication network is expected as a composite radio environment including multiple Radio Access Technologies. Therefore, how to select an optimal network for subscriber to achieve Always Best Connected in this heterogeneous network environment is becoming a popular research field. In this paper, an adaptive network selection scheme is proposed. The Cobb-Douglas utility function in microeconomics is introduced to measure subscriber's satisfaction to different networks, which considers both user preference and QoS criterions. In order to test the performance of proposed scheme, two scenarios are proposed and the simulation results are given at last.