In this study we used continuous oxidizing equipment to produce carbon fiber. The results show when the stretch of the fiber during continuous oxidation is increased, the orientation and modulus of resultant carbon fiber is unexpectedly decreased. This effect is much different from other published results. In this case, the stretching occurs after the cyclization of the molecular chains in the amorphous region. The stretching leads to the scission of some cyclized molecular chains in the amorphous region and the shrinkage of the crystalline region.