Using the many body potential,we studied the rapid cooling processes of Ag under different velocity by means of molecular dynamics simulation technique,with the pairs analysis method,we analyzed the local symmetry of molecular cluster.We found that the cooling velocity is so critical that not only the presence,but all so the structure of crystallization is determined by it.In the process of crystallization,we found the rebuild of the local cluster and the transformation of pairs from 1661?1441 to 1421?1422.We also gave other important information of the microstructure of Ag.In the end,we concluded that the F S potential worked very well to the cooling process of noble metal.