Based on pore structure theory, a device for measuring the wetting properties of materials was designed. The effect of recycled aggregate replacement rate, and water reducer, expansive agent, fly ash dosage on isothermal absorption of recycled aggregate concrete was investigated. Through curve fitting, the function relationship of isothermal absorption curve of recycled aggregate concrete with different mix proportion was established. It is proposed that the water contact angle can be calculated from the initial absorption curve, and its impact on drying shrinkage of recycled aggregate concrete is analyzed. Research results show that the addition of recycled aggregate and superplasticizer lowers the contact angle of recycled aggregate concrete, and increases the drying shrinkage. The addition of fly ash improves the pore structure of concrete, and can reduce the wettability, which can help inhibit the shrinkage of recycled aggregate concrete; It is difficult to explain the shrinkage mechanism of expanded recycled concrete only from material wettability and pore structure theory.