The invention discloses application of has-mir-195-5p used as a biological marker for preparing lung cancer diagnostic reagent kits and application of has-mir-195-5p inducers to preparing medicines for treating lung cancer. The application has the advantages that as shown by results obtained by means of lung tissue or blood detection, expression of the has-mir-195-5p in normal population is obviously higher than expression of the has-mir-195-5p in lung cancer patients, accordingly, the lung cancer patients and high-risk population can be accurately recognized, and normal individuals can be excluded; as discovered by diagnostic research and analysis, the expression level of the has-mir-195-5p is high in sensitivity and specificity and large in area (larger than 0.75) under working curves ofsubjects when the has-mir-195-5p is used for diagnosing lung cancer, and accordingly the has-mir-195-5p has a high diagnostic value as compared with the traditional biological markers.