Grid computing is regarded as a viable next-generation computing infrastructure. GridRPC, an RPC mechanism tailored for the Grid, is one of the most attractive and easiest programming models on the Grid. Ninf-G version 1 is a GridRPC system developed by AIST Grid Technology Research Center, and released on 19th, November 2002, as an open source software. Ninf-G provides library functions and system commands which can be used for development and execution of application programs on the Grid. We will continue the R&D of Ninf-G as a reference implementation of proposed standard GridRPC API at the Global Grid Forum.