We have developed a new method of passivating the surfaces of mercury cadmium telluride (MCT) by growing anodic oxidation films in a pulse mode. A novel equipment of pulse anodic oxidation was designed and developed successfully. The interface obtained by this method was superior to that grown by the traditional constant current. The influence of pulse oxidation on MCT surface was investigated by means of SEM, AES and photoconductivity decay. The optimum pulse oxidation condition to reduce the surface recombination velocities has been investigated. The mechanism of the growth of pulse oxidation film is analyzed and discussed.