By carrying forward the research fields and priorities in the previous Blue Book of Big Data，the report focuses on the application of big data for governmental，civil and commercial use，and makes rational assessment of the big data development levels of different cities through further revision and improvement of the index evaluation indicator system. On the whole，the gaps in big data development among major cities are constantly narrowing down，with different cities all making progress. In terms of geographical distribution，from 2016 to 2019，cities in the eastern，central and western regions were all gaining momentum in the development of big data year by year，while the northeastern region was slightly on a decline. In terms of the classification of big data development，the number of cities of one-side dominated application and balanced application is on the rise，while that of low-level balanced application is gradually reducing，with governmental use still being the major type of big data development. Different regions have seized the opportunity of big data，with steady progress being made in its overall development.