The invention discloses a method for preparing black fungus all-component protoplasm by utilizing cellulase. The method comprises the following steps: cleaning black fungus, removing photosensitive substances on the surface of the black fungus, drying and adding purified water; and stewing in a high-pressure steaming device, cooling the stewed black fungus, and finely milling fully, standing, and defoaming so as to obtain black fungus stoste; carrying out ultrasonic treatment on the obtained black fungus stoste, and adjusting the pH value; putting the black fungus stoste after adjusting the pH value into a constant-temperature water bath pot, heating, adding cellulase, carrying out water bath at constant temperature for 1 hour, and carrying out centrifugal filtration treatment; regulating the temperature and the pH value of the enzymatic supernate, and carrying out enzyme deactivation treatment. After the black fungus is subjected to enzymolysis by cellulase, the dissolution rate of the cellular content is improved, so that active substances such as polysaccharide are completely released into enzymatic hydrolysate from cells, the problems of complex operation, long operation time, active structure damage and low yield of the traditional black fungus processing technology are solved, effective ingredients in the black fungus are obtained simply and efficiently, and the functional components are protected.