The invention discloses an unsaturated soil suction force measurement device based on a filter paper method; the unsaturated soil suction force measurement device includes a soil sampling pipe, a casing pipe, a measuring pipe, a filter paper inserting device, a small soil cutter, and a filter paper separating device. The soil sampling pipe and the measuring pipe are embedded in the casing pipe; the upper end of the casing pipe is provided with a rubber ring, and a half-ring opening is formed in the middle-upper part of the casing pipe. Filter paper is placed in the filter paper inserting device and is inserted into the half-ring opening of the casing pipe, the filter paper inserting device is drawn out, and the measuring pipe is pushed to make a soil sample cling to a soil sample; after the filter paper is balanced with water vapor of soil for a period of time, the filter paper is taken out, the water content is measured, and the suction force in the soil is calculated according to the water content of the filter paper and a suction force curve.