To investigate the effects of different planting patterns on the grain size distribution of water-stable aggregates，the contents of organic carbon and nitrogen in aggregates with different grain sizes，and the contents of soil microbial biomass carbon and nitrogen in red soil，field experiments were carried out on inter-cropping maize (Zea mays L.) with soybean [Glycine max(L.)Merr.]and radish(Raphanus sativus L.)respectively，as well as sole-cropping systems of these three crops.Crops were sampled at their mature stage.The results showed that: in the treatments of inter-cropping systems of maize//soybean and maize//radish，and sole-cropping systems of maize，soybean and radish，the percentage of macro aggregates(＞0.25 mm)was significantly higher than that of micro aggregates(<0.25 mm)，and the percentage of macro aggregates with grain size of 0.25～2 mm was significantly higher than that of the other two kinds.The percentage of macro aggregates was shown as: maize//soybean>maize//radish>sole-cropping maize>sole-cropping radish>sole-cropping soybean，while the percentage of micro aggregates performed the opposite.As for the amount of organic carbon，aggregates with 0.25～2 mm grain size occupied the most，followed by those with grain size less than 0.25 mm，and those with grain size bigger than 2 mm contained the least.Maize and soybean inter-cropping contained the most organic carbon while sole-cropping maize contained the least.The distribution of total nitrogen content was as same as organic carbon in aggregate fraction，but the total nitrogen content of sole-cropping was higher than that of inter-cropping.C/N ratio for organic carbon to total nitrogen of inter-cropping was higher than that of sole-cropping，and C/N of grain size >2 mm was higher than that of the other two kinds. The distribution trend of microbial biomass carbon and nitrogen in aggregate grain size was consistent，both showed that the content of inter-cropping pattern was higher than that of sole-cropping pattern，and the content of macro aggregates was higher than that of micro aggregates.As for the C/N of microbial biomass of carbon to nitrogen，the sole-cropping pattern was higher than that of the inter-cropping pattern，and micro aggregates were higher than macro aggregates.Compared with sole-cropping，inter-cropping could improve the content of water-stable macro aggregates in soil，increase the content of organic carbon and nitrogen，and the content of microbial biomass of carbon and nitrogen in the grain size of macro aggregates.