Institute of Industrial Science, University of Tokyo (IIS) has started a project to develop the fundamental technologies for constructing new-generation seafloor geodetic observation system. The current observational method using research vessel cannot help being subjected to annual cruise schedule of research vessels. It has been difficult for us to change the cruise schedule as appropriate according to weather and sea condition, GPS satellite distribution and so on. The new system, which we are developing, based on AUV technology will give us opportunities for observation with choosing favorable conditions of sea and GPS satellite distribution, much more frequent observations and flexible planning of observation in response to sudden geodetic events. Trial models of the sea surface and seafloor units were finished. We conducted several performance evaluation experiments in the sea and dam site, in order to bring the observation system to completion.