A YBa2Cu3O7-δ thin film is modified by a probe electric field of an atomic force microscope to form a ridge with the width of only a grain cell. The modification varies with the operation parameters of the bias voltage,the moving velocity of the probe and the ambient humidity. Energy dispersive spectroscopy analysis shows only oxygen deficiency in the modified YBCO thin film. As a result, the suppressed superconductivity was found in the junction crossing the ridge.