This research aimed to: 1) develop an arithmetic interactive training system for elementary school students; and 2) evaluate the effectiveness of the developed system. The system was designed using the System Development Life Cycle framework and implemented as a web application incorporating interactive video-based learning, pre-post-assessments, and automated certification issuance. Development tools included PHP, Angular, HTML, CSS, and MySQL. The research instrument consisted of 1) an arithmetic interactive training system and 2) a system efficiency evaluation form. Data were analyzed using descriptive statistics, specifically the mean and standard deviation. The results of the study revealed that: 1) The system operates through two main components: user interface and administrator interface. The user interface comprises the following functional modules: system membership, mathematics thinking training, training performance reports, and profile management. and 2) The system's performance was evaluated by five experts in educational technology and mathematics using blackbox testing. The results revealed that the overall system effectiveness was rated at the highest level (= 4.64, S.D. = 0.48), particularly in functional requirements, usability, integration, and performance. These findings indicate that the system is highly effective in supporting the development of foundational arithmetic skills for elementary students.