To ascertain the effect mechanism of high temperature after anthesis on rice quality,the experiment was conducted with two rice lines,the heat-tolerant line 996 and heat-sensitive line 4628,with high temperature and optimal temperature in the growth chamber to investigate the effect of high temperature stress after anthesis on rice appearance quality,milling quality,cooking and eating quality and starch granule structure of endosperm. The result showed that milled rice rate,head rice rate,amylose content and gel consistency of both lines decreased under high temperature stress after anthesis,while the ratio of grain length to width,chalky rate,chalkiness,protein content increased. Under high temperature treatments,gelatinization temperature,final viscosity,set back and peak time increased,breakdown decreased,Mg content and K content increased,Mg / K ratio decreased. Under same treatment,the extent of rice quality of heat tolerant line 996 affected by high temperature was lower than that of heat sensitive line 4628. Under high temperature stress after anthesis,starch granule arranged untightly,most of starch granules existed in the form of a single starch endosperm,refractive index decreased,transparency reduced,and led to the formation of chalk. Under high temperature stress after anthesis,the increase of protein content,the decrease of Mg / K,the changes of rice RVA profile characteristics and starch granule structure of endosperm could be the main reason for the decrease of rice cooking and eating quality and appearance quality. To ascertain the effect mechanism of high temperature after anthesis on rice quality, the experiment was conducted with two rice lines, the heat-tolerant line 996 and heat-sensitive line 4628, with high temperature and optimal temperature in the growth chamber to investigate the effect of high temperature stress after anthesis on rice appearance quality, milling quality, cooking and eating quality and starch granule structure of endosperm. The result showed that milled rice rate, head rice rate, amylose content and gel consistency of both lines decreased under high temperature stress after anthesis, while the ratio of grain length to width, chalky rate, chalkiness, protein content increased. Under high temperature treatments, gelatinization temperature, final viscosity, set back and peak time increased, breakdown decreased, Mg content and K content increased, Mg / K ratio decreased. Under same treatment, the extent of rice quality of heat tolerant line 996 affected by high temperature was lower than tha t of heat sensitive line 4628. Under high temperature stress after anthesis, starch granule arranged untightly, most of starch granules existed in the form of a single starch endosperm, refractive index decreased, transparency reduced, and led to the formation of chalk. Under high temperature stress after anthesis, the increase of protein content, the decrease of Mg / K, the changes of rice RVA profile characteristics and starch granule structure of endosperm could be the main reason for the decrease of rice cooking and eating quality and appearance quality.