In order to study the allelopathic effects of Wedelia trilobata on Capsicum annuum var. grossum, the aqueous extract from the leaves and stem of Wedelia trilobata were prepared, and the germination of Capsicum annuum var. grossum seeds were treated with different concentration gradient, exploring different parts and the concentration aqueous extract of Wedelia trilobata to promote or inhibit the effect on germination and growth of Capsicum annuum var. grossum. The results showed that the germination rate, germination index and vigor index of Capsicum annuum var. grossum seeds decreased with the increase of aqueous extract concentration from leaves and stem of Wedelia trilobata. And each index reached the lowest when the treatment concentration reached 0.5 g/mL. The inhibitory effect of aqueous extracts from the aerial parts of Wedelia trilobata on the germination of Capsicum annuum var. grossum seeds was stem＞leaf. The fresh weigh of the seeding increased with the increase of the concentration of aqueous extract at the beginning, but decreased with the increase of the concentration of aqueous extract after the fresh weigh of the seeding reaching the maximum（11.14 g and 6.82 g）.