The invention discloses a method and device for testing the gas content of a shale gas reservoir. The device for testing the gas content of the shale gas reservoir comprises a high-pressure nitrogen inlet device, a high-pressure natural gas inlet device, a first six-way valve, a booster pump, a second six-way valve, an evacuator, a thermostat, a rock core desorption flow model, a pressure sensor, a ring crush control pump and a gas metering device, wherein the high-pressure nitrogen inlet device and the high-pressure natural gas inlet device are connected with the second six-way valve by virtue of pipelines after passing through the first six-way valve and the booster pump; the evacuator is connected with the second six-way valve; the second six-way valve is connected with the gas metering device by virtue of a pipeline after pasting through the rock core desorption flow model arranged in the thermostat; and the rock core desorption flow model is respectively connected with the pressure sensor and the ring crush control pump which is used for performing follow-up control on the ambient pressure of the rock core desorption flow model. By adopting the device disclosed by the invention, the shale gas desorption in the development process of a gas reservoir is researched by virtue of a physical simulation method, and the gas production rate during shale gas exploitation is measured.