The non-uniform corrosion morphology of steel bars is the key to determine the mechanical properties of corroded steel bars. The accelerated corrosion method of ‘electroosmotic-constant current-dry-wet cycle’ and 3D scanning technology were combined to obtain the corrosion morphology of 13 steel specimens with different corrosion degrees and diameters. The effects of corrosion degree and steel diameter on the mechanical properties were studied through monotonic tensile test and numerical simulation. The results show that the nominal yield strength， nominal ultimate strength， nominal elastic modulus， hardening initial strain and nominal peak strain of steel bars decrease with the increase of corrosion degree， and the strength characteristic value of small diameter steel bars is more significantly affected by corrosion. However， the analysis results of micro-section method show that the deterioration of nominal mechanical properties of corroded steel bars is caused by the weakening of cross-sectional area， and the actual mechanical properties do not change. According to the test data and simulation results， the degradation law of each mechanical property parameter is calibrated with the maximum cross-section corrosion rate and the average mass corrosion rate as the quantitative indexes of corrosion degree， then the tensile constitutive model of non-uniform corroded reinforcement is established.