Rosa roxburghii fruit is a good source of high quality dietary fiber. This research was to determine the content and composition of dietary fiber during the development of ‘Guinong 5’ R. roxburghii fruit and its response to light. The results showed that： (1) during the whole development of the fruit, the percentage of total dietary fiber and insoluble dietary fiber increased in the young fruit stage 40 days after anthesis, and then decreased continuously with the rapid development of fruit, showing a consistent trend of change and accounting for 24% and 16% of the dry weight of fruit at the time of maturity, respectively. However, soluble dietary fiber changed steadily during the fruit development, and remained at about 8% of the dry weight. (2) Dietary fiber components such as cellulose, hemicellulose and lignin also showed a continuous downward trend during the whole development of the fruit, while pectin had a rapid accumulation process 20 days after flowering, and cellulose and hemicellulose were the main components of the fruit when maturing, accounting for about 60% of the total dietary fiber. From the changes of the total amount of dietary fiber and its main components in single fruit, the main period of dietary fiber accumulation in R. roxburghii fruit was 60 days after anthesis. (3) The analysis of monosaccharide components of dietary fiber showed that galactose and glucose were the main total dietary fiber and insoluble dietary fiber, while mannose was the main soluble dietary fiber, showing great differences. Fruit bagging and shading promoted the accumulation of soluble dietary fiber and lignin in different degrees, but had no significant effect on total dietary fiber, insoluble dietary fiber, cellulose and hemicellulose in fruits. (4) The content of dietary fiber was higher in the young fruit stage, and then continued to decrease with the development of the fruit. Shading can promote the accumulation of lignin and soluble dietary fiber.