The present application relates to a sampling device for geotechnical engineering drilling and exploration and a sampling method thereof, and relates to the technical field of sampling equipment, which improves the problem of low soil layer testing accuracy. There is a mounting column sliding between the top seat and the base, a cylinder is provided on one side of the mounting column, the cylinder is provided with a contact plate, the top seat is provided with an air pump, the mounting column is provided with a connecting rod, the mounting column is provided with a connecting hole, and the connecting rod slides on the The connection hole, the installation column is provided with a closed groove, the closed groove slides with a closed column, and the closed column is provided with a through hole; the base is provided with a driving plate, the connecting rod is provided with a sampling half-cylinder, the sampling half-cylinder is provided with a support plate, and the sampling half-cylinder is provided with The chute is provided with a closed half cylinder, the sampling half cylinder is rotatably connected with a rotating shaft, the rotating shaft is fixed with a transmission gear, the closed half cylinder is provided with a tooth slot, the rotating shaft is fixed with a rotating gear, and the installation column is provided with a rack. The present application has the effect of improving the accuracy of soil layer testing.