The invention discloses an osmosis device capable of realizing a variable-water pressure function, and belongs to the technical field of civil engineering. The osmosis device comprises a variable-frequency circulating water supply system and a testing and measuring system, wherein a PLC (programmable logic controller) control cabinet and a frequency converter control water pump to provide variable-frequency water pressure, and a water pipe, a tee and a ball valve can realize the circulating water supply function; the testing and measuring system comprises a testing section, a differential pressure transmitter, a flowmeter, a signal converter, a computer and the like; the pressure sampling point of the testing device is positioned in the axis, and is in a belt hole round shape; the differential pressure transmitter, the flowmeter, the signal converter and the computer are mutually connected, so as to automatically collect water pressure difference and water flow rate. The osmosis device has the advantages that the variable-water pressure function is realized, the water pressure difference can be automatically measured by the differential pressure transmitter, and the higher measuring accuracy and wider measuring range are guaranteed; the defects of larger error, waste of water resources and the like in the traditional osmosis device are overcome, the testing process is convenient and rapid, and the result is reliable.