The invention relates to a monitoring method for determining terminal temperature difference of a heater of a regenerative system of a power plant steam turbine, which comprises the following steps: 1)collecting data; 2)calculating data and 3)detecting and displaying. The calculating method is carried out through comprehensive consideration, the calculated terminal temperature difference data of the heater combines a unit real-time running state for giving a correction early warning, so that a complex unit operation system can provide a reasonable and accurate correction prompt, so that economical efficiency for power plant operation is increased.