Nucleosides are essential building blocks of RNA and other related biomolecules.Normal metabolism of RNA generates free nucleosides, which can be reused to build new RNA.However, abnormal cell status such as cancer cell generation will produce nucleosides with different kinds of medication.As modified nucleoside can not be used to assembly RNA, they are released to urine.Thus, urinary modified nucleosides can be used as potential biomarkers for early detection of cancers.As modified nucleosides are present in very low concentration at early stage of cancer development, their specific and effective enrichment is a key and challenging step for early detection of cancers.