The invention discloses a ventilation control system for a laboratory. The system comprises a main air inflow pipe, an air inflow pipe branch, an air inflow device, a main exhaust pipe, an exhaust pipe branch and an exhaust device and is characterized in that an air adjusting heat exchange segment used for adjusting the air flow and heat exchange is arranged on the exhaust pipe branch and located in the air inflow pipe branch; the air adjusting heat exchange segment comprises a connecting shaft, a first torque motor, a rotating bearing, a gear sleeve, a transmission gear set and connecting cylinders, and the connecting cylinders are sequentially arranged from left to right. In the rotating process of a plurality of inner air adjusting heat exchange fins, a spiral channel can be formed, the size of the channel and the size of an opening of the channel change regularly, and therefore the air flow of the exhaust pipe branch can be adjusted, and in a similar way, the air inflow of the air inflow pipe branch can be adjusted; in the rotating process of the inner air adjusting heat exchange fins, the contact area of air in the channel and the inner air adjusting heat exchange fins is unceasingly increased, and therefore heat exchange between the exhaust pipe branch and the air inflow pipe branch can be achieved through the inner air adjusting heat exchange fins and outer air adjusting heat exchange fins, and the temperature difference of air in the exhaust pipe branch and air in the air inflow pipe branch is reduced.