Research on the application of metal nitrides in catalysis and adsorption of pollutants in water is gaining increasing attention. The M-N bond is usually formed between metal and nitrogen in metal nitrides, in which covalent, ionic, and metallic bonds constitute the predominant bonds which to a larger degree influence the properties of metal nitrides, especially the bond between transition metal and nitrogen atom changes the coefficient of metal lattice. Adjusting the d-band within the metals, can improve the material properties such as electrical conductivity, chemical stability, electrocatalytic performance and mechanical stability. In this review, we sought to systematically introduce the synthesis of metal nitride, the different classes from the point of source. We also analyzed the advantages and disadvantages of various synthesis methods and their application in capacitive deionization (CDI) and electrocatalysis. Finally, we have also shed light on the modification of metal nitrides and how each modification influences the material mechanism.