Data processing system for JT-60 is constructed by mini-computers, microcomputers and CAMACs for the control and the data acquisition of plasma diagnostics. However, it is difficult to apply this system to the remote diagnostics using the internet, because the old microcomputers used for over 15 years has no internet connectivity. Therefore, the data processing subsystem using mini-computers and microcomputers should be replaced, keeping the consistency with the main computer. The workstation based on UNIX-OS is a useful candidate for replacing those computers, since it is excellent in the network communication, the cost and the stability. We therefore the replaced microcomputers controlled and monitored the diagnostic CAMAC system, and executed its data acquisition. The new workstation-based system was simple system, which consisted of the serial highway driver module for controlling CAMAC and CPU module with SPARC CPU in VMEbus. By these replacements, the difficulty in the remote control has been solved by using the network and screen control of X Window. The maintainability is also improved and the function enhancement becomes easier. In this paper, basic design for replacing mini-computer and microcomputer with the UNIX workstation will be described.