The invention discloses application of an LILRA2 gene as a molecular marker for diagnosing multiple myeloma. Through adoption of a gene chip, a QPCR experiment shows that an LILRA2 gene expression product has significant difference between expression in normal myeloid tissue and expression in multiple myeloma tissue, namely the detection of expression condition of the LILRA2 gene in the myeloid tissue can be used for determining whether a tested person suffers from multiple myeloma or has the risk of suffering from multiple myeloma. A kit for diagnosing multiple myeloma is developed according to the relevance between the LILRA2 gene and the multiple myeloma; the kit can be applied to early diagnosis of diseases and has an extensive application prospect in clinic. In addition, the invention also discloses application of the LILRA2 gene as a molecular target for treating multiple myeloma and provides the basis for development work of medicines for treating multiple myeloma.