Abstract: Pore scale is the key to the recovery of coalbed methane reserves. Incomplete flowback will significantly affect the permeability and ultimate recovery factor of coalbed methane. To address the issue that the key controlling factors and synergistic effects governing fracturing fluid retention at the pore scale remain poorly understood, this study investigates the retention mechanism of fracturing fluid in coal reservoirs at the pore scale. Based on two-dimensional pore structures of real coal cores acquired via scanning electron microscopy（SEM）, a multi-field microscopic flowback model at the pore scale is developed by coupling the Navier-Stokes equations and the Cahn-Hilliard equations. The liquid-phase retention characteristics, the evolution of preferential flow channels, and the multi-factor coupled influence mechanism during fracturing fluid flowback are systematically analyzed. By combining high-precision pore network modeling and two-phase flow dynamics simulation, the dynamic characterization of the microscopic retention mechanism of fracturing fluid in coalbed methane reservoirs is achieved. The results show that the residual fracturing fluid exhibits four typical spatial distributions: dead-end, continuous, film-like, and cluster-like morphologies, among which film-like and cluster-like retention are the dominant residual patterns. The fluid pressure gradient is small in large pores, whereas the flow velocity increases significantly at narrow pore throats accompanied by a pressure jump. Interfacial wettability controls the residual saturation of fracturing fluid via capillary force: the residual saturation on hydrophobic surfaces（θ＞90°） is 44.50 percentage points lower than that on hydrophilic surfaces（θ＜90°）. A smaller contact angle markedly enhances capillary pressure, which acts as the driving force in the early flowback stage. Increasing the two-phase viscosity ratio（M） optimizes fluid seepage characteristics and reduces flow resistance: the residual saturation at lgM = −2.00 is 8.79 percentage points lower than that at lgM = −2.69. Reducing surface tension effectively weakens capillary trapping, and the residual saturation is 18.03 percentage points lower than that in the high-surface-tension system. The results reveal the gas-liquid two-phase flow dynamic behavior and interfacial evolution mechanism during fracturing fluid flowback under the condition of multi-physics coupling, providing a theoretical basis and technical support for the optimization of efficient coalbed methane recovery technologies and the development of high-performance fracturing fluids.