Newly designed magnetic-alloy/noble-metal FeCo/Pt nanorods have been first reported and fabricated through a length-controllable catalyzing-synthesis process in' which the growth of FeCo nanorods was induced on Pt nanotips. The length of FeCo/Pt nanorods depends on the number of platinum nanotips. The proposed synthesis mechanism was corroborated by scanning electron microscopy, transition electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. With the decrease of Fe content in FexCo96-x/Pt-4 nanoalloys from 77 to 15, the morphology changes from nanorods with different lengths to nanoparticles. The analysis of the magnetic hysteresis loops indicated that the magnetic saturation and coercivity were strongly dependent on the length of the nanorods in which maximum saturation magnetization and minimum coercivity were obtained for Fe77Co19/Pt-4 nanorods with the length of similar to 2.5 mu m. In particular, FeCo/Pt exhibited length-dependent reactivity towards 1,1,2,2-tetrachloroethane, and Fe77Co19/Pt-4 nanorods with the length of similar to 2,5 mu m yielded the greatest dechlorination rate. Moreover, Pt can enhance the dechlorination of 1,1,2,2-tetrachloroethane.