Study on the distribution of organic and inorganic cementing materials in different sizes of water stable aggregates in diameter of >5, 3-1, 1-0.5 and <0.25 mm separated from latosols, latosolic red earths and red earths by using a method of orderly sucessive removing the colloid from aggregates was carried out. Results show that with the increase in activity of clay particles and with the decrease in content of inorganic cementing material after exploitation of red soils the water stability of aggregates and the soil structural coefficient are decreased. These parameters, however, can be gradually increased in the application of organic material under the rational fertilization and management of soil. The relation of structural stability of red soils to soil tonality was also discussed. The strengthening structural stability of red earths in middle subtropics by application of organic material is more important than in tropical latosola.