In this article, the field-emission property of individual CuO nanoneedle was investigated to explore its tip image and real work function using in situ transmission electron microscopy. The maximum emission current of nanoneedle used in this study was 1.08 mu A, and two different slopes in the corresponding F-N graph existed with work functions of the CuO nanoneedle being 1.12 and 0.58 eV. In comparison with the single CuO nanoneedle, the field enhancement beta and parameter s of the CuO nanoneedle's film arrays were also studied, which showed that the screening effect played a key role in the field-emission process.