Water-repellent soils, existingwidely in nature, havesome important effects on soil environment and crop growth. In order to analyze water repellency of sand and clay, models of sand and clay different in particle size were built. Results showed that no phenomenon of water repellency was found in sand soil when the contact angle of water with sand was small. Water repellency of sand soil was closely related to soil water content when the sand-water contact angle was big. Compactness of the soil was another important factor affecting soil water repellency. When the sand soil was highly compacted,whether the soil was hydrophilic or hydrophobic wasvery sensitive to water content, and it might switch from one state to another with changing soil water content. When the sand soil was quite loose, it was no longer sensitive to soil water content. In clay soil with soil-water contact angle being slightly less than 90°and wetting radius b being small, the phenomenon of water repellency was observed. But when the clay soil was much smaller than 90°in soil-water and bigger in wetting radius b, it was hydrophilic. When the clay soil was quite high in soil water content, soil-water contact angle was the factor determining soil water repellency.