Abstract: The gas-water relative permeability is one of the critical parameters that determine the industrial value of coalbed methane (CBM) reservoirs. Measuring and estimating the relative permeability of CBM reservoir is the underlying problem that needs to be solved urgently to promote the industrialization of CBM. Based on the current research on gas-water relative permeability at home and abroad, this paper summarized the research progress from the three aspects including the experimental method, theoretical model, and numerical simulation. And four understandings were obtained: ① the unsteady-state method is more widely used in the measurement of relative permeability of CBM reservoirs, but the effect of in-situ temperature is still less studied. The microfluidic experiments hold great promise in visualizing and quantifying flow behavior of multiphase fluids. ② The improvement of the experimental device combined with emerging technologies such as nuclear magnetic resonance imaging and CT scanning experiments can visualize the fluid displacement process and achieve the test results more accurately. However, the in-situ conditions of the formation is difficult to restore during the experiment. And the accuracy and stability of the sensor still need to be further improved. ③ Although various models for calculating the relative permeability in CBM reservoirs have been established, there are different assumptions and scopes of application, and the universality still needs to be further verified. Besides, the geometry of the real pore-fracture structure is not taken into account in the models. ④ Numerical simulation can break the limited sample size in physical experiments. And the dynamic characterization of the permeability change process can be realized combined with the field development data during enhanced CBM recovery. Finally, this study points out that ① we should further expand the test environment of gas-water relative permeability to in-situ reservoir temperature conditions; ② explore the flow behavior of multi-type mixed gas and water phases; ③ establish a unified test procedire for microfluidic experiments and expand its application scenarios and geological connections; ④ deepen the linkage analysis and application of numerical simulation and physical experiments.