The comprehensive evaluation index system of digital economy development level in Gansu Province is constructed from four dimensions of digital infrastructure, digital application, digital transformation and digital innovation ability.The index weight is determined by using the entropy method, the development level of digital economy in Gansu Province from 2015 to 2020 is evaluated. The relationship between the digital economy and its sub-systems is analyzed by using the grey relational grade, and establishes the grey forecasting model to forecast the future development trend of the digital economy Gansu Province. The results show that the development level of digital economy in Gansu Province is increasing year by year, but the development of each subsystem is unbalanced, and the digital application is the main driving force for the development of digital economy in Gansu Province.The contribution of digital innovation to digital economy is low, which is the main weakness of digital economy development in Gansu Province at present.