The invention discloses a testing device and testing method for textile warmth retention performance in a low temperature environment. The device consists of a test module, a data transmission and regulation modulate, and a data processing and output module. The test module includes a stirrer, a test cup, a stirring rod, a temperature sensor and a heater. The test cup is sealed overall, and the stirring rod, the temperature sensor and the heater are placed inside the test cup. The stirring rod is connected to the stirrer. The data transmission and regulation modulate consists of a PID adjustment apparatus and a heating power regulator. The PID adjustment apparatus is connected to the temperature sensor. The heating power regulator is connected to the heater. The PID adjustment apparatus isrespectively connected to the heating power regulator and temperature sensor. Compared with the traditional warmth retention performance testing, the method provided by the invention can simply simulate the human body environment at low temperature and more visually and accurately represent the textile warmth retention performance in a low temperature environment, and is simple and practicable.