Objective To investigate the anticancer mechanism of Herba Hedyotis Diffusae on PG cell by observing the action of Herba Hedyotis Diffusae in inducing apoptosis of PG cells. Method After treating PG cells with different doses of drug containing serum of Herba Hedyotis Diffusae, FCM was used to detect the apoptosis of PG cell. Result After treating PG cell with Herba Hedyotis Diffusae, typical apoptosis characteristics could be seen and apoptosis rates were increased with the relation of dosage-effect, which were 6.86%, 9.77% and 11.69%, respectively. Conclusion Inducing the apoptosis of tumor cells maybe part of the anti-tumor mechanism of Herba Hedyotis Diffusae.