The invention provides a measuring device of hydraulic characteristic parameters of unsaturated soil in a moisture absorption/desorption path, which comprises a pedestal, a sample container, a semi-permeable membrane, a silk screen, a weighing device, an accommodating bottle, a water inlet pipe, and a water outlet pipe; the sample container is provided with a chamber for accommodating a soil sample to be measured; a cover plate is disposed at the top of the sample container; the chamber of the sample container is tightly fastened with the pedestal; the silk screen is disposed on the pedestal; the semi-permeable membrane is layed on the silk screen; a soil water potential measuring instrument is disposed on the pedestal; a peristaltic pump is disposed at the water inlet pipe; the water inlet pipe and the water outlet pipe pass through the pedestal; one end of each of the water inlet pipe and the water outlet pipe is communicated with the chamber, and the other end of each of the water inlet pipe and the water outlet pipe is communicated with the accommodating bottle; the water inlet pipe is also provided with the peristaltic pump. The device of the invention controls the suction and the moisture absorption/desorption path of the soil sample by dialysis technology, prevents the influence of wetting front, shortens the measuring time, and can measure hydraulic characteristic parameters of unsaturated soil in the moisture absorption path. The invention also provides a measuring method of hydraulic characteristic parameters of unsaturated soil.