Recycled composite powder concrete was prepared by mixing recycled brick powder and recycled concrete powder to replace part of the cement. Sulfate attack tests and microstructure characterization under dry-wet cycles were carried out to analyze the pore structure parameters and the evolution process of interfacial transition zone. Based on its microstruture evolution process， SO42- attack model was established， which revealed the deterioration mechanism of recycled composite powder conclete under sulfate attack. The results show that compressive strength loss rate of the recycled composite powder concrete decreases and then increases with the increase of the number of dry-wet cycles， and the change is greater with the increase of the replacement rate of recycled composite powder. The recycled composite powder with low replacement rate has played a better role in filling effect and nucleation to promote cement hydration， but the initial defect of high porosity provides a large number of attack channels， which is the main reason for the accelerated deterioration of the durability performance of recycled composite powder concrete.