【Objective】Rice is a staple food for the people in China, so it is feasible to improve effectively the status of the Chinese people being generally insufficient in intake of selenium by increasing the content of selenium in rice grains. Therefore, it is of great practical significance to the country to study characteristic of Se absorption and accumulation by rice, to define critical periods of the crop absorbing and accumulating selenium, hence to effectively regulate Se intake with daily diet. Rice is a species of hydrophyte, growing for a long time in fields flooded with water, where poor in areation, the crop has a well-developed aerenchyma formed at the root, to adapt itself to the anaerobic environment. The aerenchyma releases oxygen into the rhizosphere of the rice, which acts jointly with rhizosphere microorganisms to form a thin layer of "iron coating" on the surface of the root. The coating readily adsorbs selenium, thus lowering its bio-availability. As the researches in the past focused mainly on kinetics of Se absorption by rice at the seedling stage and impact of the iron coating on Se absorption and transfer, little has been reported on Se absorption and accumulation by rice at different growth stages, and impact of the iron coating on rice root on Se absorption and accumulation in the whole growth period. 【Method】A pot experiment was carried out to study Se absorption by rice at various growth stages and accumulation in various parts of the plant, and mechanism of the iron coating on rice root surface affecting Se absorption and accumulation. 【Result】Results show that the jointing stage was the period of time when the nutritive organs of rice grew and accumulated the rapidest in biomass to store adequate nutrients for the growth of reproductive tissues of the rice at the next growth stage, namely, booting stage. Se content in the nutritive tissues varied with growth stage, and peaked in the root at the jointing stage. Se in the root and stem was transported to the other parts of the rice at the booting and maturing stages. About 50% of the selenium in the various tissues was absorbed by the plant at the jointing and booting stages, and 47.22% of the total selenium in the spikelets was filled up at the booting stage. Obviously, jointing and booting stages are the two critical periods for the plant to absorb and accumulate selenium in. Se content in the iron coating peaked at the seedling stage, accounting for 73.63% of the total in the plant, which was 4.87 times that (15.12%) in the stem. As the plant grew, Se content in the iron coating declined significantly down to 20.02% in proportion at the maturing stage, while Se content in the stem reached 65.42%, which shows that in the entire life cycle of rice, the iron coating on the root surface is able to accumulate a certain amount of selenium through sorption and serve as a Se source for the plant at the late growth stages, when soil solution contains less selenium. The selenium adsorbed to the iron coating can be absorbed and transported by the plant to its shoots. So the iron coating on the root surface plays a role of "buffer" in the process of Se absorption and transport. 【Conclusion】By illustrating Se absorption and accumulation by rice varying with growth stage, this study has defined that the jointing and booting stages are the two critical periods for the crop to absorb and accumulate Se in and the iron coating on the root surface plays a role of "buffer" in Se absorption and accumulation of rice. All the findings in this study may have certain theoretical and practical significance in producing selenium-rich rice grains.