The invention relates to a device for using a descending method to detect the viscosity and the density of dense media suspending liquid, belonging to the detection technical field. The device is used for carrying out online automatic detection to the viscosity and the density of the dense media suspending liquid. The technical proposal is as follows: the device consists of a feeding automatic switch valve, a feeding pipe, a constant pressure shunt box, a detecting pipe, an overflow pipe, a differential pressure membrane and a secondary instrument, a discharging automatic switch valve and a collecting box; the feeding automatic switch valve is arranged on the feeding pipe; the detecting pipe and the overflow pipe are arranged below the constant pressure shunt box in a vertical and parallel way; and the lower ends of the detecting pipe and the overflow pipe are introduced to the collecting box; the side wall of the central part of the detecting pipe is provided with the differential pressure membrane and the secondary instrument; and the discharging automatic switch valve is arranged at the joint of the detecting pipe and the collecting box. The invention can directly measure the viscosity of the suspending liquid, eliminate the radiation hazard of density measurement, reduce the wear of the suspending liquid to be detected to the sensor and influence of flowing rate of the suspending liquid to be detected to measurement, and has the advantages of high measurement precision, strong stability, convenient use and maintenance and no potential safety hazard.