The development of the digital economy is conducive to the innovative development of foreign trade and the formation of a “dual circulation” development pattern in China. Based on the panel data of 285 prefecture-level cities in China from 2005 to 2019, this paper examines the influence of the digital economy on urban export trade and its heterogeneity. And we use a mediating effect model to explore the possible mediating role of technological progress in the above influences. The results find that: (1) The improvement of the digital economy can promote cities export; (2) The promotion of the digital economy to the growth of city export scale is heterogeneous, which is more significant in the western and northeastern cities with relatively remote geographical locations, and the third-tier and lower cities with relatively backward economic development. (3) Technological progress has played a significant role in promoting the growth of export for the digital economy. Thus, it’s of great importance for China to increase investment in digital economy infrastructure and pay more attention to the differences in diverse city development processes. It should also support basic research and development in information technology to promote high-quality development of China’s foreign trade through the digital economy.

China’s rare earth export trade has developed so rapidly since 1990s that China has gradually occupied a leading position in the international market. However, this fast development was proceeding at the cost of the rare earth energy consumption and environmental devastation. Now China begins to attach great importance to environmental protection, which attracts many researchers. This study aims to analyze the influence of environmental regulation on China’s rare earth export trade. And the original study is amongst the few to examine the relationship between environmental regulation and China’s rare earth export with the product-level data. Different from previous studies, this paper selects China’s rare earth export data from 1995 to 2015 and introduces product heterogeneity based on the rare earth production process. Moreover, this study uses the entropy weight method to measure the intensity of environmental regulation. The core conclusions are as follows: (1) Environmental regulation significantly promotes rather than restrains China’s rare earth export. (2) According to the rare earth production process, this paper divides rare earth products into 3 kinds, that is, rare earth raw materials, rare earth useful components and rare earth end-use applications. Then, it is found that rare earth useful component export in processing and smelting is positively affected by environmental regulation. Rare earth raw materials and end-use applications in China’s export are hardly affected. (3) Technological innovation has a mediating effect on the impact mechanism of environmental regulation on China’s rare earth export, which means that environmental regulation significantly promotes technological innovation of enterprises, and thereby the rare earth export is increased. The findings are helpful for policymakers to resolve the issue of environmental devastation.