We are developing a thermophysical property database by collaboration of scientists, researchers, and engineers who produce data by measurement and/or evaluation [1]. The independent databases in personal computers of collaborators are merged to a master database file stored in the database server operated at the key station and opened to worldwide access via the Internet. This system will encourage data registrants to construct their own databases and accumulate thermophysical property data for huge variety of materials. A user friendly graphical user interface has been developed to register and access thermophysical property data the internet efficiently as shown in Fig.1.