We developed the seafloor acoustic ranging system to monitor the seafloor crustal movement. In 2008 September we carried out an observation to monitor the active splay faults on Kumano-Nada prism slope. We deployed three PXPs with about 925 m (M1-S2 baseline) and 725 m (M1-S2 base line) spacing at the depth of 2880 m. We recovered three PXPs in 2010 August. Data set is the acoustic measurement for 6 month and the pressure measurement for 18 month In March 2009, very low frequency earthquake activity near the experiment area was observed by OBSs, which was deployed by JAMSTEC and ERI. We didn't observe the change of baselines in this system. Therefore we have a assumption that there was no crustal movement that exceeds the detection sensitivity in this event.