Finite element method is an usual modelbuilt method,in which the reduction transaction is necessary for the acquired model as it has a larger degrees of freedom(d.o.f.),and generally speaking, the first several eigenvalues and eigenvectors can be accurately gained.In the paper, a new dynamic condensation method is presented based on the eigenvalues and mastermodepart (the parts corresponding to master d.o.f. in eigenvectors),and the reduction model obtained by Guyan reduction can be updated by aid of an iterative method,the eigenvalues and mastermodepart. Compared with congeneric other methods, the presented method has a higher calculation precision, smaller calculation efforts and better calculation stability. In the last, an example is given to show the effectiveness of the presented algorithms.