Severe Fever with Thrombocytopenia Syndrome virus (SFTSV) is a tick-borne pathogen associated with high mortality, particularly among the elderly, and poses a significant public health threat in East Asia's rural areas. Improved diagnostic approaches are crucial for effective disease management in resource-limited settings. In this study, we developed a portable Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) platform for rapid and accurate SFTSV detection. Primers targeting the conserved L gene were designed using 158 sequences collected between 2019 and 2023, and a multiplex assay incorporating the β-actin gene as an internal control to verify amplification efficiency in alignment with clinical performance requirements. We assessed the assay's sensitivity and specificity, ultimately establishing the RT-LAMP platform in a portable, clinical-grade device. The RT-LAMP assay achieved a detection limit of 500 RNA copies per reaction and provided results within 20 min. It demonstrated high specificity without cross-reactivity with other pathogens. Performance comparisons with commercial qRT-PCR kits using clinical specimens confirmed the RT-LAMP platform's reliability. The newly developed RT-LAMP platform is a rapid, accurate, and cost-effective diagnostic tool for SFTSV with strong potential for point-of-care testing (POCT). Its portability and ease of use make it ideal for application in resource-constrained environments, thereby enhancing SFTSV surveillance and improving public health outcomes in affected regions.