Abstract: For throttling admission steam turbine units, operation with large regulating valve opening may improve the unit economic performance but lower its primary frequency regulation capability. In this paper, through the test data analysis and the variable condition calculation, the primary frequency regulation performance curve is obtained for the 1 000-MW steam turbine units. In addition, the sliding pressure curve and the valve opening high limit curve which meet the primary frequency regulation standards are also presented. Considering the practical performance test results, the net coal consumption rate is calculated for the operation conditions of qualified primary frequency performance and 45% regulating valve opening. The results show that by improving the main steam pressure and sacrificing some economic performance, the primary frequency regulation performance of the throttling admission steam turbine units can meet the requirements of related standards.