The real time change of surface morphology during the RF magnetron sputtering Ta<SUB>2</SUB>O<SUB>5</SUB> films on Si substrates was studied by the fixed angle X-ray reflectivity measurement. During the early stage of polycrystalline Ta<SUB>2</SUB>O<SUB>5</SUB> growth, the surface roughness change reveals a surface morphology of island nucleation and island coalescence processes. After the thickness of 7 nm, the surface roughness increases up to more than 2 nm at the thickness of 80 nm. For crystalline Ta<SUB>2</SUB>O<SUB>5</SUB> films, the density of the sputtering Ta<SUB>2</SUB>O<SUB>5</SUB> films was also increased and reaches the value of bulk value only when the thin film thicker than 80 nm. For the amorphous sputtering film, the surface roughness is smoother and density is smaller.