Fe doped up-graded and down-graded PST thin films were prepared on Pt/Ti/SiO2/Si with sol–gel method. Crystal structure and surface morphology of graded PST thin films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). The dielectric measurements were conducted on metal-insulator-metal capacitors at the frequency from 100 Hz to 1M Hz and at room temperature. It was found that the up-graded PST thin film had a larger dielectric constant and lower figure of merit (FOM) than the down-graded film. At 1M Hz, the tunability of up-graded PST thin film was about 65.48%, which was higher than that (about 41.84%) of down-graded PST thin film. The FOM of up-graded and down-graded PST thin films were 16.3 and 9.2, respectively. Our results showed that the dielectric tunable properties of the Fe doped graded PST films depended strongly on the direction of the composition gradient of the graded PST films.