Provided are an application of an exosome-associated microRNA in the preparation of a diagnostic and predictive lung cancer marker and a kit using the same. The present invention develops a PCR platform miRNA-based two-step detection kit, which combines an up-regulating molecular marker and down-regulating molecular marker, has outstanding advantages in the auxiliary diagnosis of lung cancer, and has a minimum sensitivity of 1 copy/μL, greatly improving detection accuracy. In addition, the present invention develops a one-step detection system based on miRNAs in isothermal amplification technologies, more rapid and convenient than conventional technologies, so as to greatly improve detection efficiency and reduce detection costs.