Abstract: In order to analyze the change rule of hydrophobic degree of soils with the addition of different hydrophobic agents, the sandy soils hydrophobized by sodium lauryl sulfate (SDS), silane coupling agent KH-550 (SCA KH-550) and dichlorodimethylsilane (DCDMS) were prepared respectively along with the clays hydrophobized by octadecylamine (OCT) for the soil test in this study. The hydrophobic degree of different hydrophobized soils and the relevant change laws were obtained by water drop penetration time (WDPT), the molarity of an ethanol droplet technique (MED) and the contact angle measurement method (CAM) respectively. The mixtures of sandy soils and DCDMS according to the proportion of 100 g: 3 mL were obtained, which showed an extreme hydrophobicity. The contact angle of these mixed soils was 78.33o, which reached to subcritical hydrophobicity and it can be kept stable for a long time. This modification method can be an optimal way for preparing the hydrophobized sandy soils. A mixed liquid of SCA KH-550, ethanol and deionized water with the volume ratio of 3:15:2 were obtained firstly. Then the mixtures of natural sandy soils and this mixed liquid with the proportion of 100 g: 25mL were obtained finally. The hydrophobicity of mixed soils was small initially, then was enhanced with the time increasing and reached to the highest finally. The contact angle of these mixed soils was 65.99o. However, these mixed soils were easy to clump and showed a poor uniformity and dispersibility. That meant this modification method was not recommended for preparing the hydrophobized soils. A mixed liquid of SDS and pure acetone with the proportion of 1 g: 10 mL were obtained firstly. Then the mixtures of sandy soils and the liquid with the proportion of 100 g: 50mL were obtained finally. These mixed soils showed little hydrophobicity all the time. The contact angle of mixed soils was 35.5o. Moreover, the process of modification was complicated and time-consuming. Thus, this modification method was not suitable for preparing the hydrophobized sandy soils. The mixtures of clays and OCT in different ratios were prepared with deionized water together firstly. Then the hydrophobized clays were obtained finally by drying, pulverizing and sifting in an order of particle sizes. The severity ratings of hydrophobized clays were moderate, severe and extreme with 0.2%, 0.3% and 0.6% OCT contents, respectively, and all of them can be kept stable in hydrophobicity all the time. Moreover, the severity ratings of hydrophobized clays can be still high with the increasing of OCT contents. That meant the hydrophobized clays do not need high OCT content and a best content of it was 0.5% content in our test. Besides, OCT had little effect on both environment and humans. It was seen that this modification method can be used as an optimal way for preparing the hydrophobized clays. The mixtures of modified clays with 0.5% OCT content and natural sandy soils in different ratios were prepared. No hydrophobicity was shown in the mixture with less than 3% hydrophobized clays content. However, its penetration time was longer than the natural sandy soils'. That meant the hydrophobized clays played a role in hydrophobicity. The severity ratings of mixtures were moderate with 3% - 10% hydrophobized clays content and severe with 10% - 50% hydrophobized clays content. The results can provide a reference for the further analysis on hydrophobized soil and its application in engineering.