The strengthening preloading is an economic,effective and easy to implement strengthening measure,which can greatly improve the fatigue strength of chain,and it can replace ordinary preloading,which can not greatly improve the fatigue strength of chain. In the chain manufacturing process,the chains must be preloaded to ensure early broken,because of chains have not enough static strength,will not happen in normal use. The preloading process should be according to the different working condition of the chain,though process test,choosing science,reasonable preloading force and preloading time.