The invention discloses a device for monitoring temperature and pressure of a slow cook-off test and a method. The device comprises a temperature sensing array, a pressure sensing device, a data acquisition unit, a computer, a voltage-stabilized direct-current power supply, a constant-temperature box and a closed container arranged in the constant-temperature box, wherein the temperature sensing array comprises a plurality of temperature sensors, the temperature sensors and the pressure sensing device are all installed on an outer wall of the closed container, the temperature sensors are uniformly distributed in the axial direction of the closed container, and the temperature sensors are used for detecting a temperature field in the closed container; and the computer collects signals fromthe temperature sensors and the pressure sensing device in real time through the data acquisition unit, and displays and stores the signals, and the voltage-stabilized direct-current power supply is used for supplying power to the temperature sensors and the pressure sensing device. The device for monitoring the temperature and pressure of the slow cook-off test and the method can monitor the temperature and pressure of the slow cook-off test in the closed container in real time so as to meet the requirements of users.