Abstract: As China's infrastructure enters the operation and maintenance stage from large-scale construction, economical and effective non-destructive testing (NDT) methods are urgently needed for the identification and diagnosis of structural defects. Solar Loading thermography (SLT) is a passive thermal imaging technique that refers to infrared thermography conducted under outdoor conditions considering the influences of solar radiation and other environmental effects. SLT has the characteristics of non-contact and lightweight, and has attracted widespread attention from scholars at home and abroad. This paper analyzes and summarizes its fundamental mechanisms, detection modes, and influencing factors. It also presents major research applications in infrastructure maintenance domains including building facades, roads and bridges, and wind turbine blades. Furthermore, prevalent thermal image processing techniques and defect identification methodologies are reviewed and compared. some directions requiring further investigation are presented to advance SLT applications in infrastructure NDT.