Based on the concept analysis of digital economy，this paper focuses on the fundamental supporting role of Information and Communication Technology（ICT）in the digital economy，starts from ICT’s techno-economic characteristics of pervasiveness，substitution，and synergy，defines the digital economy as two integral parts as “digital industrialization” and “industrial digitalization”，and constructs a framework for calculating the added value of the digital economy based on growth accounting. Based on the above，the scale of China’s digital economy from 1993 to 2019 is measured on a year-on-year basis，and an attempt is made to evaluate and forecast the scale of China’s digital economy during the 14th Five-Year Plan period. Results show that：From 1993 to 2019，the average growth rate of China’s digital economy was 16.6%，which has become an important engine for China’s economic growth；In 2019，China’s digital economy has an added value of more than 17 trillion yuan，accounting for approximately 17.2% of GDP；It is expected that during the 14th Five-Year Plan period，the average annual nominal growth rate of the digital economy will reach 11.3%. By 2025，the scale of added value will exceed 32.67 trillion yuan （nominal value），of which the added value from digital industrialization is about 15.52 trillion yuan，and about 17.15 trillion yuan from industrial digitalization. Existing measurement methods generally inherit from national economy statistics and accounting，ignoring the efficiency and utility improvement and the increase of consumer surplus derived from new business models and new models. Against this backdrop，it is necessary to go beyond value-added accounting and try new measurement methods to fully showcase the status quo of the development of digital economy.