Mid-infrared tunable diode laser absorption spectroscopy (TDLAS) has been extensively applied in high-sensitivity gas detection. Diode laser temperature control systems exert considerable influence on the comprehensive performance of gas detection systems. The overall design of temperature control systems for mid-infrared diode lasers is established in this research on the basis of the system’s structural optimization, thermoelectric cooler (TEC) selection, transfer function identification and control algorithm optimization, and the first-stage fuzzy PID combined with a second-stage PID control algorithm is applied to the actual system finally. The system can be quickly stabilized at any setting temperature between 10 °C–50 °C with a precision of ±10 m °C, and the energy consumption efficiency is high. The results lay the foundation for the optimization of the TDLAS systems’ overall performance.