Abstract: Based on the experiments of nine bias columns with 500MPa fine grain bars and one column with HRB400 bars,it was observed that the test' development of the crack and failure mode.Through the analysis of the experimental results 500MPa Fine-grained bias columns' crack width and spacing of the measured values are compared with the calculation results by the code formula.The results show that the measured value that can meet the requirements is less than the one calculated in accordance with existing norms,but the calculated values of crack width in accordance with the norm is greater.The crack width of the bias component is smaller than bending members,components by the stress state impact the crack width;calculation results of crack width by the proposed formula show that the bias component and bending members have the same reliability.