The invention discloses a siRNA for inhibiting tumor growth and oligomeric nucleic acid combination and application of the siRNA. The oligomeric nucleic acid of the invention is double-strand RNA as the following 1) or 2): 1) oligomeric nucleic acid siPTN consisting of sequence 1 and sequence 2 in a sequence table; and 2) double oligomeric nucleic acid consisting of the oligomeric nucleic acid siPTN of 1) and miR-34a, wherein the miR-34a is the oligomeric nucleic acid consisting of sequence 3 and sequence 4 in the sequence table. Tumor cells are inoculated to nude mice, and after tumors are formed, the experiment in which the oligomeric nucleic acid is used for treatment proves that the oligomeric nucleic acid combination can inhibit in-vivo growth of tumors effectively. As a novel small nucleic acid-type antitumor drug, the siRNA chemically synthesized and modified is hardly degraded, has long effect half-life, and can be used for in vitro experiment, even for in vivo treatment.