【Objective】To investigate the feasibility of using the indirect labeling method to label small molecular peptide cNGQGEQc with 188Re and to observe the inhibitory effect of 188Re-cNGQGEQc on lung adenocarcinoma cell line A549 in vitro.【Methods】188Re- cNGQGEQc and 188Re- cNAQAEQc（negative polypeptide radiolabeled with 188Re） were prepared by indirect labeling method with ethylene dicysteine（EC）as the bifunctional chelating agent. The labeling rate， specific activity，radiochemical purity（RCP）and octanol-water partition coefficient were determined，and the stability in normal human serum was evaluated. CCK- 8 assay was used to detect the inhibitory effects of 188Re- cNGQGEQc，188Re- cNAQAEQc and free 188ReO4- with different radioactive doses on A549 lung cancer cell proliferation. Then the relative in⁃ hibitory rates and 50% inhibiting concentration（IC50）of the three peptides were calculated and compared.【Results】The labeling rate，specific activity and log P value of 188Re-cNGQGEQc were（90.24±1.58）% ，（4.07±0.14）TBq ·mmol/L- 1 and（-2.90±0.03），respectively. The RCP of 188Re-cNGQGEQc purified by using a Sep-Pak C18 column and after being placed in normal serum for 24 h at 37 ℃ were（98.42±0.32）% and（89.08±0.94）%，respectively. CCK-8 assay results revealed that 188Re- cNGQGEQc significantly inhibited the proliferation of A549 lung cancer cells in a dose- dependent and positively-correlated manner. IC50 value of 188Re-cNGQGEQc was 44.88×107 Bq/L ，significantly lower than 93.45×10 Bq/L for Re-cNAQAEQc and 99.60×10 Bq/L for ReO （P<0.01）.【Conclusion】It is feasible to use EC as the bifunctional chelating agent to label small molecular peptide with 188Re and this labeling method has high labeling rate and good in vitro stability. The in vitro experiment confirms that 188Re-cNGQGEQc can effectively inhibit the proliferation of lung adenocarcinoma cell line A549. These results provide the experimental basis for further in vivo application of small molecular peptides for the targeted therapy of lung cancer.