The invention relates to a kit for auxiliary diagnosis of multiple tumors by taking a micro ribonucleic acid (RNA) combination as a tumor marker, and a detection method of the kit. The invention belongs to the fields of genetic engineering and oncology. The detection method comprises the steps of (1) extracting RNA from serum; (2) carrying out polyadenylation on the 3' end of micro RNA; (3) purifying and recovering a tailing product; (4) carrying out an inverse transcription reaction on the tailing product; (5) testing the relative expression of the micro RNA by means of a fluorescent quantitative PCR (polymerase chain reaction); (6) analyzing the result of the fluorescent quantitative PCR. The kit has the characteristics of high conservative property, space-time specificity, stability, tissue specificity and the like, and plays an important role in the aspects such as disease pathogenesis research, early diagnosis, individualized treatment and prognosis; furthermore, the kit is simple to operate, convenient in material obtaining, safe and noninvasive, and is conveniently used for screening of a great deal of diseases.