Waste-rubberized ceramsite concrete is an improvised building material that is suitable for lightweight wall panels, which can significantly reduce the bulk density of buildings. In this study, the effects of different water–cement ratios on the mechanical properties, water absorption, ultrasonic velocity, and sulfate corrosion resistance of waste-rubberized ceramsite concrete were investigated, and scanning electron microscopy (SEM) was used to study the microscopic interface. The test results show that the water–cement ratio of 0.45 is optimal. The compressive strength, water absorption rate, and ultrasonic velocity of the specimen first increased and then decreased as the water–cement ratio increased. The sulfate corrosion resistance of specimens with a high water–cement ratio is weaker than that of specimens with a low water–cement ratio. It is of great significance to explore the optimal water–cement ratio of the waste-rubberized ceramsite concrete for further research, and it has important production guidance significance for commercial applications.