In this article, the bending deformation of stainless steel fibers during knitting action was investigated. Two stainless steel fibers with different configurations were knitted into plain knitted fabrics on a flat knitting machine. During the knitting action, the formation of needle loops were recorded and analyzed by using the image processing approach. The curvature radius of the needle loop was examined and regressed with polynomial fitting. The experimental results indicate that stiffness is the main factor affecting the bending deformation. Yarn diameter and needle geometry are another two important factors influencing the bending deformation.