Abstract: The present invention discloses an application of an exosome-related microRNA in preparing a marker or diagnosis and prediction of lung cancer and a kit, and develops a PCR platform-based two-step detection kit for miRNA, which has the outstanding advantage in the aspect of auxiliary diagnosis of lung cancer by the combined use of up-regulated and down-regulated molecular markers, and has the sensitivity as low as lcopy/?L, greatly improving the detection accuracy. In addition, the isothermal amplification-based one-step detection system for miRNA developed by the present invention is faster and more convenient, which can greatly improve detection efficiency and reduce detection costs.