Learning difficulties are problems that can hinder students' learning outcomes, so they need to be identified early. This study is motivated by the diagnosis process of student learning difficulties at MTsN 6 Agam, which is still done manually, making it difficult for Guidance and Counseling teachers to quickly and systematically identify students' learning difficulties. This study aims to apply the forward chaining method in developing a web-based student learning difficulty diagnosis system to support the diagnosis process and provide handling recommendations. This research uses the Research and Development (R&D) method with the Waterfall model, consisting of the stages of Communication, Planning, Modeling, Construction, and Deployment. The system is developed using native PHP, MySQL, and Bootstrap. Testing includes Black Box Testing to examine system functionality, validity testing using Aiken’s V, and practicality testing using Moment Kappa, and tested for effectiveness using the G-Score. The study results showed a validity value of 0.97, which falls into the valid category, practicality of 0.85 categorized as very practical, and effectiveness of 0.82 in the High-g category. Black Box Testing results showed that all system functions ran according to requirements. Thus, the developed system is considered valid, very practical, effective, and feasible to be used as a supporting tool for BK teachers in diagnosing students' learning difficulties at MTsN 6 Agam.