The quality of Portland cement significantly influences the performance of concrete [1–۳]. Existing standards do not specify the shelf life of Portland cement. However, invalidation of Portland cement is likely to occur due to the influence of environmental conditions. While the compressive strength of Portland cement is 5 MPa lower than the standard compressive strength, mechanical performance of cement will not be up to standard [4]. As a result, the compressive strength of concrete by using invalidated cement cannot be guaranteed, and quality-related safety accidents could frequently occur [5–۷]. Therefore, invalidation characterization of Portland cement is necessary. In the research on the invalidation characterization of Portland cement, visual observation and strength test methods have been mainly used. The visual observation method is used to detect severe caking on cement surface according to a phenomenological empirical experience. Chen [8] classified agglomeration during cement storage classified into three categories: warehouse caking, pile caking and bag caking. Furthermore, they provided suggestions for preventing agglomeration of Portland cement by controlling the content of C3A in the clinker. However, no quantitative parameters of the corresponding relationship between the content of C3A and invalidation of Portland cement were presented. The compressive strength test method is used to determine cement invalidation by testing the compressive strength of 28-day cement mortar specimens and examining whether the strength of the cement meets the specifications. However, this method exhibits strong hysteresis. Zou [9] utilised energy-dispersive spectrometry (EDS) to determine the types and contents of elements in mineral constituents in montmorillonite powder to determine which varieties of montmorillonite drugs fail. He [10] utilised scanning electron microscopy (SEM), EDS and X-ray diffraction to analyse and characterize the corrosion invalidation products on the steel structures of a substation. The results showed that the corrosion invalidation of steel structures was caused by the electrochemical corrosion of carbon steel in humid atmosphere. Inspired by the above two research in different fields and so on, we think that the microscopic detection is very useful for the quantitative invalidation characterization of Portland Cement. Therefore, a quick and accurate method of quantitative invalidation characterization of Portland cement was proposed in this study by using microscopic analysis methods, such as BSE and EDS, to investigate the microstructure’s morphological change and the invalidation essence of Portland cement.