Heat furnaces are nonlinear models. The characteristic of thermal furnaces is the thermal inertia stage. The furnace reaches the temperature it needs to supply, taking quite a long time. Currently, there are many algorithms that can be applied to control this furnace, typically the PID algorithm. There are typical methods for finding PID parameters such as the first and second Ziegler-Nichols methods. In addition, there is a distinction between continuous PID and digital PID (discrete). In the article, the author studies the method of controlling digital PID at Ho Chi Minh Technical Pedagogical Research Department. The algorithm is effective through Matlab / Simulink software simulation and experiments on real models.