Abstract: Time-space consumption method is one of the most essential methods for calculating the capacity. To promote the accuracy of the calculation result and cope with the defect of traditional method that neglects vehicles' operating heterogeneities on different levels of the road, a graded time-space consumption method was proposed. The space headway is a key parameter that is the basis for obtaining reasonable results so that the calibration method for space headway is proposed incorporated with the efficiency theory. The functional relationship between efficiency and space headway was obtained associated with Van Aerde traffic flow model. For road network in Beijing, based on the proposed model, the space headways of vehicles operating on express ways, arterials and sub-arterials were obtained and they are 27.92, 25.56, and 21.88 m, respectively. Finally, taking the new planned Beijing sub hub, core area of Tong Zhou district (155 km²) as case study, the total road network capacity of arterial and sub-arterial was calculated by using the modified time-space consumption method and the result is 0.56-0.60 million pcu times per day according to the data from investigation.