This study aims to evaluate the antitumor effect of Adonis multiflora, one of the plants in the Ranunculaceae, on mice to which hepatoma cells were transplanted and to suggest its possibility as a candidate natural substance to replace antitumor drugs. We performed the MTT assay to assess the extract had a decrease in the growth rate of hepatoma cells depending on concentration. In particular, 100 ㎍/㎖ of the extract showed 40% of growth retardation rate. We assessed the autophagy activity to identify the inhibitory autophagy mechanism of tumor cells in the extract. This proved that the activity increases more as the concentration of the extract is higher. We conducted the Western blot test to confirmed the expression of two proteins LC3 and p62. The expression of p62 was in inverse proportion to the concentration of the extract whereas LC3-Ⅱ increased more as the concentration of the extract was higher. This showed that an increase in the autophagy relies on the conentration of the extract. We performed a test to discover the influence of the extracts on hepatoma cells transplanted to mice. The test proved that the extract triggers a significant decrease in the growth rate of tumor cells. Compared to the start of the test, the size of tumor cells with 50, 100 and 200 ㎎/㎏ of the extract respectively increased by 4, 3.7 and 3.5 times whereas in the controlling group by 6.3 times. The size of tumor cells in benign tumor controlling group increased by 3.1 times. This showed a significant decrease in the growth rate of tumor cells compared to the controlling group. We carried out the experiment of influence of the extract on the expression of two proteins LC3 and p62 in the tumor tissue transplanted into mice. The experiment showed that LC3-II increases more as the concentration of the extract is higher. However, there was a rapid decrease in p62 with 200 ㎎/㎏ of the extract compared to the controlling group. In this study, we proved that the autophagy activity of Adonis multiflora extract inhibits the growth of hepatoma cells by in vitro and in vivo experiments. In conclusion, the inhibitory autophagy mechanism of tumor cells in the extract can be used as a new treatment of antitumor.