Abstract: This paper presents an experimental study on the swelling and shrinking property of clay treated with STW type stabilizers. The experimental results indicate that STW type stabilizer can reduce the swelling and shrinking property of clay effectively. The sizes of soil particle and the content of STW type stabilizer have different effects on the swelling and shrinking property of the treated clay. The expansion of the treated clay with an average particle size of 0.75 mm reaches the lowest value. The swelling and shrinking property of the treated clay decreases as the content of STW type stabilizer increases. Finally, the paper discusses the mechanism of the STW polymer soil stabilizers in modification of the clay swelling and shrinking property.