In order to explore the mechanical degradation mechanism of concrete in the Erjiaokou water gate project under loaded initial damage，macro and micro mechanical tests of concrete were carried out under simulated conditions of artificial precast cracks and corrosive environment. The influence characteristics of precast crack depth，soaking time and other factors on the mechanical properties of concrete were analyzed. The results show that the influence of confining pressure on the strain development of specimens is greater than the factor of precast crack depth. When the depth of the prefabricated crack exceeds 15mm，the mechanical degradation effect of the specimen gradually appears.With the extension of soaking time，the bearing stress level of the sample decreases significantly，especially after soaking for 48 hours，the deterioration is more significant. The CT image data displays that the greater the depth of prefabricated cracks，the more internal pores there are in the sample，but the dominant pore size range is always between 500 and 2000 μm. In contrast，the longer the soaking time，although the number of pores will increase，the more variability dominant range of pore size it has. The research results have reference value for the evolution of concrete damage and anti-corrosion design.