In pursuing high emission current density and high brightness, it is difficult to avoid vacuum breakdown in nanowire cold cathode systems, which will shorten the lifetime of the electron sources. Therefore, investigations on the vacuum breakdown process are important for semiconductor nanowire point electron sources. In this study, non-catastrophic breakdown phenomena that could extend the lifetime of the nanowire electron source were observed in the field emission processes of individual defective WO3-x nanowires. In this non-catastrophic breakdown process, only part of the nanowire emitter was destroyed. After the breakdown, the remaining part of the nanowire could still emit electrons, and due to the shortening of its length, the maximum field emission current density of the remaining nanowire was increased. These results are consistent with the prediction given by theoretical calculations. A defect-related electrical transport induced breakdown mechanism and Nottingham effect induced cooling effect were proposed to be the main causes of this phenomenon. Our work provides an approach for designing long lifetime semiconductor nanowire point electron sources.