Abstract: In this paper,by the use of the Reissners variational principle,the functional of thin plates with Consideration of transverse shearing deform atio u for mixed FEM has been derived.The mixed element in a modified mixed triangular element which has 12 degrees of freedom in which a Parabolically varyi ng lateral displacement distribution and a liearly varying moment have been assumed.This kind of mixed element can be used on shells also.For a preliminary implementation for some eases of plates and shellus of engineering purposes,this new element shows merits that(1)it is more accgurate than the Herrmann,s modle of mixed FEM.(2) rates of convergence of displa cements and moments are about the same.and (3) the transverse shear of the Plate is predominant.