Disclosed is a use of methylation sites as a disease diagnosis marker, in particular relating to a use of methylation sites in a Y chromosome as a prostate cancer diagnosis marker. More particularly, the method and criterion for screening methylation sites in chromosomes associated with a disease are established in the present invention, and using prostate cancer as an example, six methylation sites in the Y chromosome associated with the prostate cancer diagnosis are screened out. Methylation sites in the Y chromosome screened can be used for early and rapid diagnosis of the disease as a prostate cancer diagnosis marker.