This book is composed in four chapters the first part consists of a generality and an overview on functionally graded materials "FGMs", the second part aims to present a general study on the different theories of plates and FGM plates, in the third part we have a review of previous research work on the functionally graded materials "FGMs" and finally the presentation of analysis of sandwich plates FGM with porosities using of high order shear-deformation theory.