An experiment was carried out to investigate effects of wheat straw extract and wheat straw decomposition liquid on seed germination and seedling growth of rice, and to define allelopathic effect of wheat straw on rice. The straw used in the test came from mature wheat crop. Wheat straw extract was prepared by putting wheat straw in 30 ℃ pure water for extraction for 48 h, and wheat straw decomposition liquid was prepared by immersing wheat straw in 30 ℃ water for incubation for 7 or 15 days. The rice seed germination test was carried out using the plate culture method and the rice growth test using the sand culture method. Results show that compared with the control, the extract and the liquid both decreased seed germination index, plant biomass, chlorophyll content and root activity of the rice, significantly (p<0.05), while increasing malondialdehyde content in the plant, significantly (p<0.05). The liquid demonstrated stronger allelopathic effect than the extract, wheat leaf extract than stem extract, and the 15 day liquid than the 7 day liquid. Once diluted five folds, the extracts and liquids became less in their effect on rice germination and plant growth. The extracts and liquids were all quite high in total phenolic content, ranging from 90.80~222 mg L^-1. Total phenolic acid content was significantly and negatively related to rice plant fresh weight, root activity, chlorophyll and rice germination index, while malondialdehyde content in the plant was positively related. The allelopathic effects of the extracts and liquids varied in strength, which was related with straw decomposition method, different parts of straw and length of decomposition time, and to the total phenolic acid content in the extracts or liquids, as well.