Particle-free conductive ink was prepared, taking silver citrate as conductive metal precursor, sec-butylamine as complexing agent and ethanol as media adjusting the viscosity and wettability. The ink could be printed on PET substrate by gravure printing, and silver conductive film with high electrical conductivity was obtained after thermal treated at low temperature. Silver citrate, silver citrate based conductive ink and silver conductive film were characterized with EDS, STA, IR, XRD, SEM and four point probe method. The results of STA showed that the mass of the conductive ink came to constant at 132 ℃ which is much lower than that of silver citrate (210 ℃); the results of SEM and XRD showed that the silver conductive film cured at 150 ℃ was constituted by compact silver nano particles with high purity; the result of four point probe method showed that its sheet resistance was 1.83 Ω·□-1.