Abstract: To achieve high time synchronization accuracy among various testing equipments of distributed measurement and control systems,a safe and reliable time source is required.The architecture and model of the time source is analyzed firstly,and a configurable method of redundancy time benchmark is presented,which can enhance the reliability of the time source.On the basis of the method,a double mode time source based on GPS and BD system is designed.The experimental result shows that the proposed time source satisfies the ITU-T G811 criterion.The time source has been used in CDMA systems as a time benchmark now.