Abstract: Singular value decomposition(SVD)is an important topic in numerical computation.It has gained wide application in control field.And it is illustrated in this paper that the floating point arithmetic of the machine affects the accuracy of the calculation to an extent which largely depends upon the problem itself and the stability of the computing method used.Finally,the SVD theorem and some basic properties of the singular value andsingular vector are introduced.And some of its application in system control and identification are given.