YBCO superconducting films were prepared by Electron Beam Coevaporation method. All the YBCO films were annealed at 760°C in humidity range of 2.3%–9.5%. Microstructure of the YBCO thin films was analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Superconducting properties of the YBCO films were measured by electromagnetic induction method. XRD results showed that c-axis-oriented grains existed in the YBCO films. Morphologies of the YBCO films showed that all the films had a smooth and crack-free surface. YBCO films prepared at 7.3% humidity condition showed J _c value of 4.6 MA cm⁻² at 77 K in self-field.