Coalbed water plays an important role in the process of coalbed methane (CBM) generation, storage (adsorption) and production. Because integrated analysis of hydrochemical characteristics and gas geochemical characteristics can offer fresh insights into CBM origin and accumulation, this paper presents an in-depth analysis of the gas geochemistry and hydrogeochemistry characteristics of CBM coproduced water to trace in-situ CBM accumulation in the Tucheng syncline. The main gaseous geochemical parameters (C1/∑C1-5: 0.97~0.99; CHC: 38.3~72.6; CDMI: 5.1~10.5%; δ 13 C-CH4: -40.7~-43.2‰; δD-CH4: -185.8~-169.2‰; δ 13 C-CO2: -13.4~-9.3‰) indicate that thermal gas is the primary genetic type, and hydrogeochemical analysis reveals strong traces of microbial activity. Based on carbon isotope fractionation calculation of DIC-CO2-CH4 in CBM and coproduced water, we established a quantitative method for calculating biogenic methane production in CBM coproduced