The present invention discloses applications of human SAMD9L gene and a protein product encoded by the human SAMD9L gene, wherein the SAMD9L gene sequence, especially the open reading frame sequence of the protein encoded by the human SAMD9L gene, generates missense mutation, nonsense mutation, frameshift mutation and other gene structure variations with different forms in tumors so as to be adopted as the specific marker gene for liver cancer diagnosis, such that liver cancer diagnosis is accurate and rapid. According to the present invention, the human SAMD9L protein can be applied on tumor patients so as to treat or alleviate related diseases caused by SAMD9L protein deletion, nonfunction or abnormality; and the human SAMD9L gene can be over-expressed in cancer cells through the transgenic technology, or the SAMD9L protein can be supplied through the in vitro supply manner to control cancer cell proliferation and metastasis so as to achieve the tumor treatment purpose.