“子像素”级量测精度是数字影像配准算法的一个重要特性，它能充分地挖掘数字影像之潜在能力。不同的匹配算法所能达到共轭影像的配准的子像素精度等级是不同的。本文研究了相关系数最大的匹配准则所能达到的子像素量测精度。理论与实验证明：采用抛物线拟会最大相关系数邻近三个值，匹配精度能达到0.15～0.20像素的数量级。配准误差近似与信噪比成反比。 “Sub-pixel” measurement accuracy is an important feature of digital image registration algorithm, it can fully tap the potential of digital imaging capabilities. Different matching algorithms can achieve the registration sub-pixel accuracy level of the conjugate image is different. In this paper, the sub-pixel measurement accuracy that can be achieved by the matching criterion with the largest correlation coefficient is studied. Theoretical and experimental results show that using the parabolic maximum correlation coefficient adjacent to three values, the matching accuracy can reach the order of 0.15 ~ 0.20 pixels. The approximate registration error is inversely proportional to the signal-to-noise ratio.