This paper proposes a novel remote-controlled laboratory (RCL) system, which was developed by using innovative ideas and methods for applying technology-enhanced learning to secondary school science education (grade 7-9 or ages 12-14) through three iterative cycles of design-based research. This Internet-based RCL system enables learners to control and observe the server side of the laboratory equipment and to perform real-time remote scientific investigations at distant places.In this study, three iterative cycle trials and refinements were performed. First, a newly developed RCL system involving four remote experiments was initially tested by 64 undergraduate students who studied science education and web technology and were enrolled in teacher training courses. Then, a refined RCL system involving eight remote experiments were then evaluated by 32 secondary school students from a local public school as a second iterative cycle (selected electricity, plants, light and sound topics). After the refined RCL system was further refined, it was again evaluated by 35 secondary school students from another local public school as a third iterative cycle. The evaluation of these three iterative cycles was performed using a mixed research method that included achievement tests (for the second and third iterative cycles only), questionnaire survey, open-ended questions and interviews specifically developed to collect data on student understanding, perception, and implementation of the use of the RCL system.The results of the achievement tests revealed that the secondary students more comprehensively understood the related science topics. In addition, the survey results indicated that the participants believed that the RCL system and methods for conducting the experiments were appropriate and educational. Nevertheless, negative comments and suggestions for improvement were identified. Accordingly, the researcher refined the RCL system and its design principles (integration with