The invention provides a motor test method in a low temperature and low pressure environment, which belongs to the technical field of motor characteristic testing in the low temperature and low pressure environment. The method comprises the steps that a tested motor and an escort motor are placed into a high-low temperature and low pressure experiment box; the tested motor works in a motor state, and the escort motor works in a generator state; the stator current of the tested motor gradually changes from rated current of 1.5 times to rated current of 0.5 times; the stray loss of the tested motor working in the motor state is PMs; the tested motor works in the generator state, and the escort motor works in the motor state; the stator current of the escort motor gradually changes from rated current of 1.5 times to rated current of 0.5 times; the stray loss of the tested motor working in the generator state is PGs; and measurement parameters and calculation results are combined to acquire the average value of the load stray loss of the tested motor. According to the invention, the parameters of the motor in the low temperature and low pressure environment can be measured; a dual-system back-to-back method is used to test the motor in the environment; and the motor test method has a broad application prospect.