The invention discloses a dynamic testing method of the gas cut resistance of an operating fluid of an oil-gas well. The dynamic testing method comprises the following steps: (a) preparing the operating fluid; (b) determining the initial density Rho0 of the operating fluid; (c) filling a testing device with the operating fluid; (d) preheating the simulation well bottom (6) to the reservoir temperature by a temperature control device (7); (e) starting up a circulation filtration device (8), and setting the circulation displacement of the operating fluid to be QL; (f) injecting a gas with the flow rate of Qg from testing holes (1-4), and starting to time; (g) sampling from sampling holes (1-3) every 5 minutes-15 minutes, and determining the density Rhoi of the operating fluid after gas cut under the initial density testing condition; (h) calculating the declining rate Ki of the density along with the gas cut time when the gas flow rate is Qg, and the circulation displacement of the operating fluid is QL; and (i) drawing a curve that the density of the operating fluid and the declining rate of the operating fluid are changed as the gas cut time. The features of the simulation oil-gas well and the gas cut resistance of the operating fluid of the oil-gas well under the dynamic circulation condition of the operating fluid can be determined.