Abstract: The uncertainly of artificial mark locations in digital photogrammetry is badly affected by imaging system.Aiming at mark location models with overlapped zero-mean Gaussian white noise and considering the physical process of imaging,a theoretical error performance Cramér-Rao lower bound based on the uncertainty theory of mark location was derived through the theory of maximum likelihood estimation.And its corresponding confidence interval was also determined on a certain confidence level.With the same confidence level,the uncertainty of any practical locations operator can be estimated with the degree of closeness between its own confidence interval and theoretical confidence interval of CRLB.To assess the uncertainty of practical locations operator and design a new more precise mark locations operator,circular mark is taken as an example to illustrate the effects of noise level and mark size on CRLB.The results show that the precision based on CRLB can be achieved 0.015 pixel by choosing suitable mark radius and small noise standard deviation.