The invention relates to a coring device for roadbed soil and a method for installing a moisture sensor by using the coring device. The object of the present invention is to solve the problem that thesoil compactness of a portion tested by a probe in the prior art often fails to meet the compactness requirement of the roadbed, so that the test accuracy of volumetric moisture content is affected,soil core sample is prone to loose in the process of lowering a moisture sensor with the soil core sample, the moisture sensor can be damaged easily in a layered compaction and backfilling process, and water can easily enter the moisture sensor during long-term monitoring. The coring device comprises a blade body, a confinement ring, a cushion block and a plurality of top wires; the outer side wall of a annular cylinder body is provided with a limiting protrusion of the confinement ring, wherein the confinement ring is an annular sleeve body, and the confinement ring is sleeved on the top endof the blade body; and the cushion block covers on the blade body and the confinement ring. The method comprises/includes: step 1, drilling and sampling; step 2, coring; step 3, inserting the moisturesensor; step 4, assembling a core sample; step 5, installing the core sample; step 6, backfilling the soil; step 7, sealing the hole. The coring device for roadbed soil and the method for installingmoisture sensor by using the coring device are used in the field of roadbed monitoring.