Objective: To investigate the influence of human blood derived mesenchymal stem cells (MenSCs) on the effects of chemotherapy in mice with A549 lung cancer. Methods: Twenty BALB/C nude mice were taken for establishing lung cancer model, and were randomized into experimental group and control group with 10 mice in each group. The control group only received chemotherapy intervention. The experimental group was treated with tail vein injection of DiI fluorescent labeled MenSCs given by an institution (3×105/mouse). After 14 days modeling of lung cancer, mice in the two groups were killed by breaking the cervical spine and the tumors were collected. The tumor volume, tumor mass, tumor inhibition rate, double lung wet weight, tumor metastasis rate, number of tumor metastasis and metastasis inhibition rate were compared between the two groups. Results: In this experiment, 20 BALB/C nude mice were statistically analyzed, and there was no report about cases lost to follow up. On the 7th day after inoculated tumor, there were tumors in 20 mice under the right fore limb armpit. There was no significant difference in tumor growth curve between the two groups (P>0.05). There was no significant difference in the average tumor volume and average tumor weight between the two groups (P>0.05); the tumor inhibition rate was 8.4%. The double lung wet weight, tumor metastasis rate and the number of tumor metastasis in the experimental group were significantly lower than those in the control group (P<0.05); the inhibition rate was 71.8%. Conclusion: MenSCs combined with chemotherapy have certain effects in inhibiting pulmonary tumor metastasis.