In order to study the effective evaluation of speckle image quality in digital image correlation method, the quality of speckle pattern was effectively evaluated by means of the second derivative of average gray level of quality characterization parameter of speckle pattern. By analyzing the relationship between image interpolation error and the distribution of image gray information, the relationship between the second derivative of average gray level of speckle pattern and the distribution form of gray level information of speckle pattern was pointed out. In order to verify the validity of the quality characterization parameters of the speckle pattern, Fourier transform was used to translate the speckle pattern. The sub-pixel displacement of speckle pattern before and after translation was calculated by Newton-Raphson method. According to the displacement calculation results, speckle pattern with low average gray second derivative corresponded to small displacement measurement error. The results show that, the second derivative of average gray level is effective in the quality evaluation of speckle pattern. In practical application, the quality of speckle pattern should be evaluated comprehensively and effectively by combining the second derivative of average gray level and average gray gradient of speckle pattern. This study provides a reference for the preparation and selection of high quality speckle patterns.