The ClusterTech Online Platform for Emission Reduction (OPER) is an online simulation platform with a core purpose of informing short-term and long-term regional air quality management strategies. Based on the technical guidance of the Chinese Ministry of Ecology and Environment’s “Three lines and one list” policy framework, OPER integrates a regional weather model, chemical transport model, source apportionment model and a comprehensive algorithm which proposes quantified, actionable emission reduction plans. The platform assists users in determining the atmospheric environment capacity, evaluating the present condition against emission targets, and formulating appropriate control measures in the region so as to prioritize key control areas. OPER has revolutionized the traditional quantitative emission reduction method, providing an innovative approach towards regional air quality management.