The noise characteristics existing in the laser beam width measurement based on CCD camera are analyzed, and the methods of effectively restraining noise are presented. The importance of the limitation of integration area for the 4σ beam width measurement, and the method to correctly select integration area are discussed. Factors affecting the accuracy of the laser beam width measurement with CCD camera are summarized. The analyses of experimental data prove that random noise and baseline offset have great effects on the small beam width with 4σ method, and the limitation of integration area for the 4σ beam width measurement is necessary. Furthermore, the experimental results show that the optimum integration area size is 2 times of the beam width; the CCD spatial resolution has little impact on the 4σ beam width measurement in the absence of noises, that is, a few pixel data can get the correct results. Besides, the effect of high frequency random noise on the 4σ beam width measurement repeatability and the methods to improve the meaurement accuracy are discussed; the effect of baseline error on the 4σ laser beam width measurement is analyzed, and the proper method of the background map subtraction is proposed to reduce the influence of noise.