The instant disclosure described a system and method to prevent the oxidizer overheating using cold side bypass for a VOCs treatment system with series rotor, which may be used in an organic waste air treatment system. The system is equipped with a Thermal Oxidizer (TO), a First Heat Exchanger, a Second Heat Exchanger, a third heat exchanger, a First Cold-Side Transporting Pipeline, a First Adsorption Rotor, a Second Adsorption Rotor, and a Chimney. There is a Cold-Side Proportional Damper installed between the First Desorption-Treated Air Pipeline and the First Cold-Side Transporting Pipeline, or it is installed on the First Desorption-Treated Air Pipeline. When the VOCs concentration becomes higher, the Cold-Side Proportional Damper can regulate the airflow to adjust the heat-recovery amount or concentration, when treating the organic waste air, it can prevent the TO from being overheated due to high oxidizer temperature, and protect it from Thermal Oxidizer shut-down.