The invention discloses a method for measuring the compacted density of a hardcore bed. The measuring method comprises the following steps of: taking a test sample out of a region to be detected by a grouting method; then obtaining the volume of a test pit by a drainage method; desizing and measuring the mass of the test sample; and finally obtaining the dry density according to a formula so as to obtain the compacting factor. Compared with a conventional method, the measuring method has accurate measuring result and is easier to operate on site.