IF钢的性能评价很大程度上取决于其[n]值、[r]值，目前广泛采用的机械引伸计方法受环境影响较大，难以获得准确、稳定的结果。为得到准确的[r]值，同时研究试验过程中影响[r]值测量准确性的因素，对IF钢进行拉伸试验并结合数字图像相关（DIC）方法对IF钢的[n]值、[r]值进行了测定，与通过机械引伸计测量应变的方法所得结果进行比较，同时，通过DIC方法在试样不同位置添加一系列虚拟横向引伸计以分析横向应变测量位置对材料[r]值测量的影响。试验结果表明，相比于机械引伸计，DIC方法具有更高的稳定性；虚拟横向引伸计测量位置的不同导致试验结果的不同，测量位置距断裂位置越远则结果误差越大，DIC方法可以保证测量位置及结果的准确性。

The evaluation of the property of IF steel mostly depends on its[n-value]and[r-value，] and it is difficult to get the stable and accurate results because the mechanical extensometer which is widely used is severely affected by the experiment environment. To get the accurate[r-value]and research the factors which influence the measurement accuracy of [r-value]in the test， the tensile test and digital image correlation （ DIC ） method are used to measure the[n-value]and [r-value]of IF steel and the experimental results are compared with the results which are got from the mechanical extensometer. In addition， a series of virtual transverse extensometers are added at different locations of the sample by the DIC method to analyze the influence of the measuring positions of transverse strain on the measurement of[r-value.] The experimental results show that the stability of the DIC method is better than that of the mechanical extensometer. Different measuring positions of the virtual transverse extensometer lead to different experimental results， and the farther the measuring position away from the fracture location， the bigger the result error is. While， the DIC method can ensure the accuracy of the measuring position and results.