In this paper, a controller based on the idea of self-tuning control put forward by Dr.D.W. Clarke has been constructed using TP-801 single-board microcomputer as the main component. The real condition of the object being controlled has been considered. Selftuning control of cooling and temperature maintaining process of a freezer for biological research has been successfully realized. The principle of the controller, its hardware designing and software programming are briefly introduced. Parameter-selecting and other problems connected with the adjustment of the controller are discussed.The contrast of a PID digital regulator vs. the self-tuning controller in experiments with changes of teat content of the freezer and ambient temperature and sudden disturbance imposed on the controlled object is presented.