PST/Bi2Ti2O7 composite thin films were prepared by sol-gel method through heavily doping Bi3+ into lead strontium titanate (PST). The film with mono pyrochlore phase of Bi2Ti2O7 was also fabricated by controlling the Ti content in precursors. XRD, SEM and impedance analyzer measured the phase status, morphology and dielectric properties of the thin films, respectively. As a result, in the composite thin films, there was some Pb and Sr dissolved in Bi2Ti2O7, and the amount of dissolving ions decreased with the reduction of their composition in precursors. Bi4Ti3O12 impurity in crystalline Bi2Ti2O7 was due to the instability of Bi, and excess Ti in stoichiometry could make the film maintain to be mono pyrochlore phase. PST/Bi2Ti2O7 composite thin films had lower permittivity and lower dielectric loss than mono PST thin films.