Abstract: In the steam turbine thermodynamic cycle, the measuring system has provided redundant measuring points. Generally, the main water flow, the main condensate flow and the feed water pump inlet flow are chosen as the mainstream in the on-site performance calculation. In this paper, by using the data reconciliation method, the redundant flow measurement point information is taken to perform data reconciliation calculation regarding the performance data of a real power plant. Then the uncertainty changes of the calculation result are analyzed. The result shows that the data reconciliation can effectively reduce the uncertainty of the calculation result.