Abstract: In order to determine the biological function of phthalanilic acid, the effects of phthalanilic acid (266.7, 200.0 and 133.3 mg/L) on the stress-resistance physiological indexes and the yield of pepper (Capsicum annuum L.) were investigated, with brassinolides as the control. The results showed that phthalanilic acid could significantly regulate the stress resistance of pepper plants. If the concentration is 200.0 mg/L, compared with the blank control, the contents of flavonoids, total phenolics and free proline in the leaves of pepper were increased by 10.06%-21.19%, 7.42%-16.95% and 241.26%-8.46% respectively, and the content of MDA was decreased by 28.58%-52.79%. Furthermore, the activities of Superoxide dismutase (SOD), Peroxidase (POD) and Catalase (CAT) were increased by 2.31%-9.00%, 4.20%-471.72% and 34.98%-121.19%, respectively. Phthalanilic acid treatment (200.0 mg/L) could also significantly increase the yield of pepper by 13.91%, compared with the blank control. Thus, it demonstrated that phthalanilic acid could induce the stress-resistance of pepper plants and increase the yield of pepper, which is similar as brassinolides.