The adsorption of oxygen on Rh(110) was investigated by thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM). The desorption of chemisorbed oxygen was observed at 700 K to 1200 K. Above 1400 K exists another desorption peak which is attributed to subsurface oxygen. The content of subsurface oxygen in Rh(110) influences the chemisorption states on the surface, so that the desorbing character of the surface oxygen species is changed. The subsurface-state needs high preparation temperature and has not any reaction with residual gas or added hydrogen in the chamber, which clarifies its spatial isolation. The XPS result showed that the binding energy of subsurface species is higher than the one of surface oxygen. This confirms the TDS observation. The subsurface-oxygen containing surface showed in STM oxygen induced hillock-like structures.