The preparation of the polymer-derived SiC fibers involves a pyrolysis process, in which great weight loss and shrinkage are usually recorded. It causes the bend, which reduces the tensile strength of SiC fibers. The reason of the bend forming is discussed on the basis of the pyrolysis process of PCS fibers; the effect of the bend on the properties of SiC fibers is studied through mechanical analysis. The way of thermal-curing under tension or pyrolysis under tension is brought forward in order to solve the problem, then the properties of SiC fibers can be improved.