The invention discloses a method for improving the cooling capability of a large-scale heat vacuum test. The method comprises the following steps: 1, designing each heating tape of a heating cage to be in a rotatable form, and synchronously moving and positioning each heating tape, wherein one surface of each heating tape is a black paint surface; 2, installing test pieces into the heating cage in the first step, pushing to a vacuum chamber, performing vacuum-pumping to a vacuum degree smaller than and equal to 1.3*10<-3> Pa, enabling the black paint surfaces to face the test pieces, and increasing to a temperature until high-temperature maintenance ends; 3, starting cooling, controlling the heating tapes to rotate by 90 degrees, and reducing the temperature until low-temperature maintenance ends; and 4, starting to increase the temperature, controlling the heating tapes to rotate by -90 degrees, enabling the black paint surfaces to face the test pieces, recovering the heating function of the heating tapes, and repeating the third step to the fourth step until the test ends. A high temperature and a low temperature are set according to a highest temperature and a lowest temperature needed by the test pieces for test examination.