Fuchunjiang river lock expansion and improving project is featured with a large quantity of concrete pouring,complex structure and high requirements on the durability,and the concrete cracks are required to be controlled strictly.For the concrete mix proportion design,we select the best aggregate gradation based on the aggregate gradation optimization test,use a large amount of mineral admixtures by mixing concrete with slag and fly ash to reduce the dosage of cement and control the rise of concrete heat of hydration temperature;By tests,we choose the optimal sand ratio to improve the volume stability of concrete and reduce shrinkage,and improve the crack resistance of concrete.