The invention relates to a combination of miR-21, miR-24, miR-125b and miR-126 used as a lung cancer molecular marker, relates to application of the combination of miR-21, miR-24, miR-125b, miR-126 and miR-39 to the preparation of miRNA detection kit for lung cancers, and relates to a miRNA detection kit for the lung cancer. An RCR reaction system comprises positive primers and a reverse universal primer aiming at miR-21, miR-24, miR-125b and miR-126; an internal reference system comprises an internal reference miRNA-39 and a positive primer aiming at miR-39; a nucleotide sequence of the positive primer aiming at r miR-21 is shown in SEQ ID No.1; a nucleotide sequence of the positive primer aiming at miR-24 is shown in SEQ ID No.2; a nucleotide sequence of the positive primer aiming at miR-125b is shown in SEQ ID No.3; a nucleotide sequence of the positive primer aiming at miR-126 is shown in SEQ ID No.4; a nucleotide sequence of the positive primer aiming at miR-39 is shown in SEQ ID No.5; a nucleotide sequence of the reverse universal primer is shown in SEQ ID No.6. The miRNA detection kit for lung cancer is high in detection speed, convenient and high in correction rate and can assist in early diagnosis of lung cancer.