Exhaust gas recirculation control system is currently an effective measure for reducing NOx emissions in exhaust gas. Its main actuating element is a numerically controlled EGR valve, which independently and accurately controls the amount of exhaust gas recirculated to the engine. The ECU adjusts the circulation rate of the exhaust gas participating in the recirculation in a timely manner according to the working conditions of the engine. When the engine is running under load, the EGR valve opens, and a part of the exhaust gas is introduced into the intake pipe to be mixed with the new mixture and then enters the cylinder for combustion, thereby realizing recirculation. The exhaust gas fed into the intake system is optimally controlled, thereby suppressing the formation of harmful gas NOx and reducing its discharge in the exhaust gas.