The invention belongs to the technical field of geotechnical engineering and geologic engineering, discloses a cutting and sample preparation integrated device for soft rocks, and particularly relatesto a testing device and a testing method of site investigation and sampling of geotechnical engineering. A main body structure of the cutting and sample preparation integrated device comprises upperbolts, a bolt pushing rod, a sample cap, sliding slots, fixed clamping arms, rock samples, baffle plates, lower bolts, a rotating handle, a dust-proof plate, a saw blade, a movable base, a track, driving pulleys, a platform, a cutting arm, a spiral pushing handle, a sample preparation base and lateral fixed bolts. According to the cutting and sample preparation integrated device disclosed by the invention, the rock samples of different sizes can be freely and flexibly cut, the sizes are accurate, a cut surface is smooth, and the high-quality rock samples can be provided for various mechanicalproperty tests of rocks.