This paper estimates the size of the digital economy in 38 countries between 2005 and 2018 and conducts an empirical study on this foundation. The results show that the digital economy has a significant role in promoting high quality economic development, primarily through industrial digitalizaion. Further research shows regional heterogeneity in the impact of the digital economy, which is greater in developed countries. Analysis of the underlying mechanisms shows that the digital economy promotes high-quality economic development in both developed and developing countries by improving technological efficiency and technological progress. However, the effect of technological progress in developing countries is clearly weaker than that in developed countries. In addition, scale efficiency in developing countries are not strengthened by the digital economy. Therefore, high-quality economic development requires the digital transformation of traditional industries and promoting their integration with digital technologies.