Abstract: The strain measured by strain-gauge is transformed into stress, which is associated with the stress state of concrete. For high stress levels of high concrete dam, the concrete will enter the stage of plastic creep when the stress of concrete exceeds a certain limit. If the conversion is still based on the stress-strain relationship of elastic creep bodies, the calculated stress can not correlate with the real situation. This paper assumed that the concrete under high stress would produce plastic flow, and viscoplastic strain rate was calculated based on the assumption of P.Perzyna. Viscoplastic strain rate calculation formula of the maximum tensile stress yield criterion and Hsieh-Ting-Chen yield criterion was first deduced, and then calculation formula of transforming the measured strain into the stress was also deduced under plastic creep. Furthermore, the transition from measured strain to stress for high concrete dams considering plastic creep was discussed in this paper. The analysis of an example showed that a stage of stress distortion would inevitably lead to the subsequent conversion of authenticity during the conversion process from measured strain to stress by stress increment, while the stress from the conversion of the measured strain was more consistent with the actual situation under plastic creep.