Recycled concrete aggregates have large porosity, large water absorption and high crush index. The performance reduces dramatically compared with ordinary aggregates. Mechanical properties of recycled concrete aggregates could be improved by adding sugar water reducer. On the basis of the experimental studies, this paper analyzes the influences on recycled concrete setting time and its compression strength at different ages when various amounts of sugar water reducer are used. The mechanism of strength increase is also discussed on the view of porosity. The results show that sugar water reducer has a high enhancement on compressive strength of recycled aggregate concrete, which provides the experimental and theoretical foundation for the application of recycled concrete aggregates in practical engineering.