Under the policy background of carbon peaking and carbon neutralization in China, it is of great social significance and market value to carry out high-precision and long-time on-line monitoring of COS and CO2 in the process of vegetation carbon absorption. According to the needs of TDLAS detection of vegetation carbon absorption gas, a pressure control system for TDLAS detection of vegetation carbon absorption gas is designed based on TDLAS long-range absorption tank. The system uses STM32 as the main control, uses the air pressure sensor to collect the actual air pressure in the long-range absorption tank, and uses the gas proportional valve and vacuum air pump as the actuator to realize the gas replacement in the long-range absorption tank and ensure the stability of low pressure at the same time. After the gas gradient control test and field long-term stability test, the system works stably, has high control accuracy, can adapt to the field environment, can meet the needs of TDLAS detection of vegetation carbon absorption gas. The system is also suitable for other detection systems based on long-range absorption tank.