Abstract: The effects of serum containing Juglone on inhibiting the growth of A549 cells and cell cycle in vitro were experimentally researched. On the basis of seropharmacology, MTT assay was used to detect the growth inhibition of A549 cells by the interference of serum containing Juglone and to screen the best drug concentration. The effect of Juglone on A549 cell cycle was analyzed by FCM (flow cytomery) apparatus and then was verified by Western blot experiment. Experiment shows that Juglone's half-time is 136 min. Result of MTT assay indicates, by comparing 12, 24 and 48 h cell survival rates, the group with 10% high dose of serum containing Juglone has the best efficacy. Meanwhile, Juglone could induce apoptosis of A549 cells, arrest cells in S phase and improve the expression of Caspase-3. It is concluded from experiments that Juglone could significantly inhibit the growth of A549 cells, arrest cells in S phase, induce apoptosis and improve the expression of Caspase-3.