By studying the effect of nano SiO2 content on the application performance of modified recycled concrete, materials for preparing nano SiO2 and modified recycled concrete were selected, and corresponding proportioning schemes were designed to prepare concrete specimens. In the testing of application performance indicators such as compressive strength, splitting tensile strength, shear strength, total cracking area, and water seepage height, it is found that there were significant differences in the application performance of modified recycled concrete under the four nano SiO2 dosages of 0%, 0.5%, 1.0%, and 1.5%. Especially at the 1% nano SiO2 content, concrete specimens exhibit the highest compressive strength, splitting tensile strength, and shear strength, while the total cracking area and water seepage height are also the smallest, with the total cracking area per unit area decreasing to 203.1 mm2. Therefore, the appropriate addition of nano SiO2 can effectively improve the application performance of modified recycled concrete. © 2024 Inderscience Enterprises Ltd.