The invention relates to a gas multi-pass cell temperature control system and method based on self-adaptive interval PID control, and belongs to the field of gas multi-pass cell temperature control. The outer wall of a gas sample cell is wrapped by a heating film to realize heating of the gas multi-pass cell, a PT1000 resistance temperature sensor is arranged between the outer wall of the gas sample cell and the heating film to detect the working temperature of the gas multi-pass cell in real time, and heat insulation cotton is adopted for the integral gas multi-pass cell to form a heat insulation effect. Improvement is made on the basis of a traditional PID control algorithm for solving the problem of large overshoot caused by the fact that a controlled object has complex structure and responses slowly, the control process is subdivided into a plurality of intervals according to temperature deviation values, a proportional amplification coefficient, an integral coefficient and a differential coefficient are set in each interval according to the interval value and the change rate of the temperature deviation value, the adaptive interval PID control algorithm is achieved, and accordingly, the temperature is controlled quickly without overshoot. Reliable guarantee is provided for improvement of performance of a carbon dioxide isotope detection system.