The kinetics and defect trapping at the solid-liquid interface of simple metal Ag during the solidification process are investigated by molecular dynamics simulation. It is found that there exists a certain characteristic value (T*) for the interfacial temperature of metal Ag at which the growth rate reaches a maximum value. Meanwhile, the vacancy defects are predominant in the solidification process of liquids. The calculation results show that there exists a linear relationship between defect concentration and interfacial temperature. The defect concentration gradually increases with the decrease of interfacial temperature, and a transition occurs near this characteristic temperature. In addition, the defect concentration is found to be dependent on growth velocity. Above the characteristic temperature (T>T*), the defect concentration almost linearly depends on the growth velocity, and both are independent on orientations. In contrast, below the characteristic temperature (T