Contents of mica in 46 soil samples, total K in particles of different sizes in 51 soil sarriples and K weathering coefficients of 14 soil samples collected from the main zonal soils of China were determined by chemical methods, and the K-supplying potentials of these soils were also calculated. Content of mica in laterite was very low, that in red earth was more than that in laterite, but it. varied greatly with the parent materials. Content of mica in yellow-brown earth was slightly higher than that in red earth. The purple soils and soils derived from loess generally contained more than 20% of mica. Contents of mica in paddy soils derived from alluvium, lacustrine deposits and marine sedimenx ranged widely.From the relationship between contents of mica and content of total K in various fractions, it was found that the content of feldspar in the fraction<2μm was very low, therefore the total K in the fraction <2μm can be wholly calculated as Lhe content of mica, but half of total K in the fraction >10μm was the K contained in mica. In laterite, red earth, yellowbrown earth and purple soil, fine particles of mica amounted to 80-90% of total mica. While in fluvo-aquic soil, drab soil chernozem, castanozem and sierozem, the fine mica content decreased, and the coarse mica content increased, amounting to 36-47% of total mica.