The invention discloses a pressure-temperature chart automatic-calling method and a pressure-temperature chart automatic-calling system for a nuclear power plant. The pressure-temperature chart automatic-calling method for the nuclear power plant mainly comprises the following steps of: receiving pressure-temperature chart calling request information; judging whether automatic calling conditions are met or not according to the request information; and if the automatic calling conditions are met, judging the running state of a main pump and automatically selecting a corresponding pressure-temperature chart according to the running state of the main pump. The pressure-temperature chart automatic-calling system for the nuclear power plant mainly comprises a storage module and an automatic calling module, wherein the storage module is used for storing a plurality of pressure-temperature charts applicable to different working conditions; and the automatic calling module is used for judging whether the automatic calling conditions are met according to a calling request, and automatically calling the pressure-temperature chart according to the working conditions of the power plant if the automatic calling conditions are met. In the method and the system, the pressure-temperature (P-T) chart is rapidly automatically called without manual selection so as to save time and avoid manual errors in judgment.