A series of bismuth layer-structured ferroelectrics thin films Srm-3Bi4TimO3m+3(m=3, 4, 5, and 6) were deposited by pulsed laser deposition (PLD) on (001) LaAlO3 single crystal substrate. XRD and Raman studies have been performed. The more sensitive Raman spectra lead to a different understanding on the layer structure of Sr3Bi4Ti6O21 from XRD. This can be attributed to the lager c-axis constant of Sr3Bi4Ti6O21 due to more layers. More layers lead to increasing disorder in the local scale of the average grain.