Based on the tunable diode laser absorption spectroscopy (TDLAS), a fuzzy adaptive proportional-integral-differential cycle control algorithm is introduced to achieve precise control of temperature and pressure inside the cavity, and the simultaneous measurement of stable carbon isotopes in ¹²CH₄ and ¹³CH₄ gases has been achieved by utilizing TDLAS via monitoring the near infrared absorption line at 1658 nm. Examination of gas samples from various coal seams and differing locations in coal mines allows for differentiation of gas source and elucidation of the origin type of the gas based on the observed isotope abundance. The detectable concentration range for the methodology is 0.94%-83.91%, and the isotopic abundance varies from -66.75‰ to -48.32‰. This technology lays the foundation for distinguishing coal seam gas sources and judging the gas types according to the isotopic abundance, and provides a valuable tool for areas such as gas transport channel in mine, early warning for gas disaster source, coalbed methane research, and environmental atmospheric studies.