Abstract: The beam quality of a LD pumped Nd:YAG laser is measured with CCD camera system. The background characteristics of the CCD system and the influence of the size of integral box upon measurement results are investigated. The following conclusions can be derived form experimental results: (1) Background is strongly depend upon exposure time and pixel binning,while temperature has an ignorable effect upon it,whether with or without ambient light. (2) A 5%-cut is the minimum value in order to get a reasonable result.