Abstract: In this paper, the multi-variable variational principles for plate bending and plane elas-ticity are presented, which included all the boundary integral formulas. The variational principlefor plate bending covers five classes of equations of equilibrium, bending moment function-bendingmoment, curvature-deflection, compatibility, bending moment-curvature and all boundary condi-tions, in which independent variables are deflection, curvature, non-homogeneous bending moment,bending moment functions and bending ...