Waste-to-energy (WtE) incineration technology is widely used to solve the energy supply, greenhouse gas emissions, and waste generation problems in urban areas. In Taiwan, there are new laws and regulations that would affect greenhouse gas management of WtE incineration plants. This research aims to identify or raise key issues to be promoted for WtE incineration plants due to existing management systems and complex issues mixed with GHG, energy, and solid waste treatment. This study utilizes inventory analysis and social LCA (SLCA) approach on GHG management of WtE incineration plants in Taiwan to systematically identify materiality issues to be promoted. According to the results of materiality analysis for SLCA, this study generalizes four stakeholders, nine subcategories, and their 15 inventory indicators; and concludes that, among assessment results of 15 inventory indicators, three indicators are at a high level, four at a medium level, and eight at a low level. In total, 12 materiality issues are recognized. This study suggests WtE incineration plants should consider the following materiality issues with respect to priority: a systematic database and calculation methods, the goal and criteria of the laws and regulations, technology development toward circular economy and promotion activity or opportunity for local community and organization level.