According to the tentative reaction equation from single molecular reaction theory,the important parameters,such as diffusion quantity and the rate equation of chemical reaction of molten tin in the reaction process between iron and molten tin,are investigated within the range of 260~350℃.The results indicated that the diffusion quantity of active atom tin increased with the time by the expression of a(1-e-bt).When the reaction attained to a certain time and FeSn layer was somewhat thick,the maximum expansion quantity per unit area was a anstant of a,which was an infinitesimal value on account of the compound FeSn hampering the diffusion of molten tin.Moreover,the average rate equation of chemical reaction k1 and the negative rate equation of chemical reaction k-1 increased with the increasing of the temperature.The decreasing tendency of the negative rate equation of chemical reaction and the rate equation of chemical reaction becomes more obvious with time.