Abstract: A series of non-periodical and periodical continuous examinations of F content have been carried out in leaves of 8 mulberry varieties within the same mulberry orchard during spring and autumn silkworm periods from 1984 to 1987. The results show that the capability of mulberry absorption and accumulation of F varies with the mulberry varieties. Among the 8 mulberry varieties, "Husang 32* has the lowest F absorption capability, therefore, it is an excellent variety for raising silkworm. "Jianchi" and ’7311" have the highest F absorption capability, they are inferior varieties for raising silkworm, and the rests arc mediate.