A method and system for effecting control governing of a steam turbine wherein the steam chamber of a first stage nozzle is divided into a plurality of steam compartments, control valves each connected to one of the steam compartments are individually operated for controlling the flow rate of steam introduced into the turbine, and the governing of the nozzle is effected by adjusting the flow rate of steam in accordance with a load. At low load, the degree of opening of the control valves is kept constant and the turbine is driven by steam of a reduced pressure by reducing the pressure of the steam at the inlet of the turbine so as to maintain, in a low load region, the volume flow rate of steam for a high load region. To cope with a change in the value of the load, the degree of opening corresponding to a predetermined change in the value of the load is set beforehand for each control valve. When the change in the value of the load is smaller than the predetermined change in the value of the load, the degree of opening of the control valve involved is adjusted. Conversely, when the change in the value of the load is greater than the predetermined change in the value of the load, the pressure of the steam at the inlet of the turbine is controlled.