Cement-based materials in sulfate rich areas will suffer from serious corrosion after semi-immersion. To study the degradation of cement mortars with different water cement ratio (w/c) partially exposed to sulfate solution, the mass change were employed to reveal damage progress. Moreover, porosity, erosion products and SO2 4 - content were monitored to study the damage mechanism. Results indicate that the porosity, SO2 4 - content and erosion products of mortars show an augment as the w/c increases. Correspondingly, high w/c leads to more severe mass change. XRD results reveal that the deterioration of drying portion is attributed to both chemical and physical sulfate corrosion. In addition, the water-soluble SO2 4 - content in drying portions is higher than that in immersed portion, implying more serious sulfate attack in drying portion.