From the Tse-Chang Li's experiments,a noticable increse in the surface roughness was obseved when the strain applied to the PET substrate was 4%.When the strain was further increased to 6%,the surface roughness became almost asymptotic to a constant value.Also,the reflection for the coated specimens decreased with increasing strain applied to the substrate.However, the effects of Tio2 films and applied strain on transmittance are quite small.