From October 8 to 12, 2019, the Sixth International Conference on Nitrification and Related Processes was held on the campus of XMU. The conference was hosted by XMU, and over 170 scholars from 17 countries and regions participated in the activity. The nitrogen cycle with nitrification as the key process is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Research on nitrification and related processes is closely related to the productivity of terrestrial and marine ecosystems, global climate change, and environmental pollution treatment.