With regard to the analysis and application of diatoms in the marine sediments, diatom purification method, data analysis method and diatom application in environmental reconstruction were summarized. The diatom purification is composed of four main processes (removing calcium carbonate, organic and minerogenic matter, and slide preparation). For each process, frequently used methods and improvements were introduced, while their pros and cons were compared. As to the data analysis, in order to ensure statistical reliability, the essential methods and principles were represented in detail with species identification and counting, data expression and error estimation involved to reduce errors as much as possible. On this basis, the numerical method application was explained for its advantage of improving the accuracy for analysis. The applications of diatom fossils in environmental reconstruction were studied more deeply abroad, including the investigation of relationship between diatom fossils and upperwater environment, the application of diatoms from deeper core sediment for reconstructing oceanic paleoenvironment, tracing salinity and reflecting eutrophication. As far as the deficiency of the domestic research was concerned, multidisciplinary technologies and observational data were suggested to be combined into the study in order to promote the quantitative research of diatom fossils and the accuracy of environmental reconstruction.