A control system of a two-shaft gas turbine, wherein the two-shaft gas turbine comprises: a gas generator including a compressor configured to have an inlet guide vane on an air intake side and compress inlet air, a combustor configured to generate a combustion gas by combusting the air compressed by the compressor and a fuel, and a high pressure turbine configured to be driven by the combustion gas generated by the combustor; and a low pressure turbine configured to be driven by a gas discharged from the high pressure turbine, wherein a first shaft which is a shaft of the gas generator and a second shaft which is a shaft of the low pressure turbine are separate shafts from each other, and a mass flow of the inlet air into the compressor is regulated by controlling a set angle of the inlet guide vane, characterized in that the control system comprises: a first controller configured to control the set angle of the inlet guide vane based on a corrected speed of the shaft of the gas generator during low speed rotation of the shaft of the gas generator, the corrected speed having been corrected according to an ambient temperature; a second controller configured to control the set angle of the inlet guide vane to maintain a constant actual speed of the shaft of the gas generator during high speed rotation of the shaft of the gas generator; and an ambient temperature correction part configured to increase the actual speed maintained constant by the second controller in a case where the ambient temperature is equal to or more than a threshold value. a gas generator including a compressor configured to have an inlet guide vane on an air intake side and compress inlet air, a combustor configured to generate a combustion gas by combusting the air compressed by the compressor and a fuel, and a high pressure turbine configured to be driven by the combustion gas generated by the combustor; and a low pressure turbine configured to be driven by a gas discharged from the high pressure turbine, wherein a first shaft which is a shaft of the gas generator and a second shaft which is a shaft of the low pressure turbine are separate shafts from each other, and a mass flow of the inlet air into the compressor is regulated by controlling a set angle of the inlet guide vane, characterized in that the control system comprises: a first controller configured to control the set angle of the inlet guide vane based on a corrected speed of the shaft of the gas generator during low speed rotation of the shaft of the gas generator, the corrected speed having been corrected according to an ambient temperature; a second controller configured to control the set angle of the inlet guide vane to maintain a constant actual speed of the shaft of the gas generator during high speed rotation of the shaft of the gas generator; and an ambient temperature correction part configured to increase the actual speed maintained constant by the second controller in a case where the ambient temperature is equal to or more than a threshold value. a first controller configured to control the set angle of the inlet guide vane based on a corrected speed of the shaft of the gas generator during low speed rotation of the shaft of the gas generator, the corrected speed having been corrected according to an ambient temperature; a second controller configured to control the set angle of the inlet guide vane to maintain a constant actual speed of the shaft of the gas generator during high speed rotation of the shaft of the gas generator; and an ambient temperature correction part configured to increase the actual speed maintained constant by the second controller in a case where the ambient temperature is equal to or more than a threshold value.