Aiming to overcome the difficulties and inefficiency confronting citizens and enterprises in public services，a serial of “Internet+Government Services” policies have been issued by the Chinese central government with the route of “to replace human’s errand by data sharing”. So an applicable evaluation approach is needed for the government offices to measure the performance. For references，the United Nation’s e-government assessment about online services is introduced as well as several evaluations in China. Then，based on framework of the communication system model and the whole of government theory，this paper builds an evaluation approach by analyzing the business process of public services and using the time opportunity cost to measure the cost of public service. This approach try to consider many governance goals which are：reducing administration expenditure，increasing efficiency，optimizing internal processes and promoting cooperation between offices. Finally，the characteristics，applicability and limitations of this evaluation model are summarized.