Abstract: Spectral CT can produce basis materials with different X-ray energies. Subsequently, the generated basis materials can be used for qualitative and quantitative evaluation of tissue components and contrast agent distribution. This approach presents a superior ability to separate and identify imaging materials compared to traditional single-energy CT. Dual-energy spectrum technology is one of the most commonly used modes in spectrum CT, which plays an important role in clinical application. In this study, the decomposition methods of a basis material in the image domain of dual-energy spectrum CT were classified into two categories: two-material decomposition and multi-material decomposition. Finally, these methods are summarized and trend of future development is addressed.