This book constitutes the refereed proceedings of the 6th International Conference on Big Data and Security, ICBDS 2025, held in Nanjing, China, during December 5–7, 2025.The 16 full papers and 1 short paper presented in this volume were carefully reviewed and selected from 250 submissions. They are grouped into the following topics: Big Data&New Method; Artificial Intelligence&Machine Learning Security; Data Technology&Network Security.