Excessive CO2 density is one of the main reasons for poor air quality. CO2 density is non-stationary with passengers’ number changing in terminal, which brings challenge for the CO2 control system. In order to make better air quality, this paper designs a data-driven CO2 control system, which chooses adjacent elements from database and optimizes PID parameters based on CO2 density, fresh air flow and other environmental data by using parameter optimizer. CO2 control system application model is built based on MATLAB/Simulink platform according to terminal environment. Simulation results show that, the system achieves good control effect of the non-stationary CO2 density through parameters optimization online, which ensures that CO2 density in terminal is lower than 800ppm. System’s steady-stage error is less than 1%. Compared with constant air volume system, the system saves about 30% fresh air volume, which can provide reference for energy efficiency design of terminal.