With the development of information and computer technology, it is possible to monitor and analyze on-line features of large steam turbine-generator units. The energy consumption rate and the exhaust steam dryness are two important indices. Base on the analyses of those existed calculation methods for turbine varying condition, we give a sequential varying condition calculation that starts with steam extraction of the final stage or the second final stage (superheated steam condition). According to the initially assumed final stage flow, and the thermodynamic parameters before the final stage, also the backpressure, we can distinguish the flow patterns of the stage by a discriminant criteria. Then we can conduct a stage varying condition calculation of primary stage in sequence from the front final stage parameter, so the new exhaust steam enthalpy and the exhaust steam dryness can be got. So the precise energy consumption rate and the exhaust enthalpy (or the dryness) can be got easily. Obviously, without measuring the flow or the dryness, we can accurately monitor the on-line energy consumption rate and the dryness of the units.