A synthetic peptide that targets cancer stem cells is provided. The peptide consists of the amino acid sequence of anyone of SEQ ID NO: 1 to SEQ ID NO: 15. Also provided is a composition comprising said synthetic peptide with a therapeutic agent fused thereto, and a pharmaceutically acceptable carrier or diluent. Further provided is a method of screening a peptide specifically targeting to a cancer stem cell. The method comprises the steps of establishing an oligopeptide library by using a phage expression system, contacting the library with a culture of bulk tumor cells of a cancer cell line, contacting the phages which do not bind to the bulk tumor cells with a culture of cancer stem cells of said cancer cell line, and screening a peptide specifically targeting to a cancer stem cell from the phages which bind to the cancer stem cells.