The embodiment of the invention provides a soil sampling method for soil compactness detection. The soil sampling method for soil compactness detection comprises the following steps that a cut grooveis cut out in an area where soil is to be sampled, specifically, the cut groove separates soil in the cut groove from surrounding soil in the transverse direction; a soil sampler is inserted into thesoil in the cut groove in the vertical direction and moved gradually in the depth direction of the soil; after being filled with the soil of preset volume, the soil sampler is lifted off the ground; and a soil pillar in the soil sampler is taken out. According to the soil sampling process, the pre-treatment procedure of forming the cut groove is added before the soil sampler samples the soil, thatis, an interval is formed between the soil in the cut groove and the surrounding soil, when the soil sampler is inserted into the soil in the cut groove, the wall of the soil sampler extrudes the soil, part of the soil is extruded into the interval, the resistance of the soil sampler in the soil is greatly reduced, and the soil sampler can be inserted and taken out conveniently. A traditional soil sampling process is divided into a series of simple procedures easy to implement, and the work efficiency is high.