Strontium titanate (SrTiO3) submicron-fibers with perovskite structure were successfully synthesized by electrospinning method. The nanomechanical properties of synthesized SrTiO3 were investigated by the novel amplitude modulation-frequency modulation (AM-FM) method based on atomic force microscope and nanoindentation technique. The results of AM-FM show that the resonant frequency of SrTiO3 submicron-fiber is lower than that of the Si substrate, which indicates that the Young\'s modulus of SrTiO3 submicron-fiber is smaller than that of Si substrate in the range of 105-125 GPa. Nanoindentation further confirmed the results, showing a value of 104 ± 17 GPa. The atomic force microscope-based AM-FM provides us a new way to study the mechanical performance of low dimensional materials.