Abstract: In order to investigate the influencing factors on the surface roughness of titanium dioxide (TiO₂) films, deposition of titanium dioxide (TiO₂) films on K9 glass with different and the same substrate roughness was completed by ion beam assisted deposition electron beam thermal evaporation.The surface roughness of substrate and film were measured by TalySurf CCI non-contact surface profiler.The experimental results show that the surface roughness of TiO₂ film increases with the increase of substrate surface, but is always less than the substrate surface roughness, indicating that TiO₂ film has the function of smoothing base surface roughness.With the increase of deposition rate, the surface roughness of film decreases firstly and then tends to be smooth.For the substrate with a roughness of 2 nm, the change of the energy of the ion beam has little effect, and the surface roughness of the film is about 1.5 nm.With the increase of film thickness, the surface roughness of film decreases firstly and then increases.