A performance test was conducted on dredged sand found in the lower reaches of the Yangtze River and manufactured sand concrete (Dredged sand and Manufactured sand Concrete-DMC), aiming to realize the comprehensive utilization of dredged sand and expand the source of fine aggregates. We used five DMC samples with different dredged-sand content and proportions and studied their micro-structures and properties. The correlation between the microstructure characteristics and mechanical properties of the samples was evaluated. The results show that with an increase in the ultra-fine dredged-sand content, the compressive strength of the specimens first increases and then decreases. When the content of dredged sand is 25%, DMC exhibits better mechanical properties and work performance. Adding the correct amount of dredged sand can increase the density of DMC and reduce porosity, improve the uniformity of pore distribution, reduce harmful pores, improve the structure of the transition zone of the DMC interface, and optimise the phase composition, but it causes the pore morphology to decrease to a certain extent. Compared with the blank control group, excessive mixing of dredged sand can still improve the mechanical properties of DMC. The Correlation studies have proved that microstructure characteristic parameters of the DMC such as porosity can be improved by changing the content of dredged sand and realizing the improvement of DMC compressive strength.