Abstract: The meshfree discretization of a Reissner-Mindlin plate and shell is presented by using a Penalty function to impose the boundary conditions. Basing on a numerical locking test, the benefit and shortcoming of Element-free Galerkin (EFG) method, a radial point interpolation method (RPIM) and the Meshless with nodal integration for solving numerical locking are investigated. The result obtained show that the meshfree method with the matching approximation fields scheme and stabilized conforming nodal integration (SCNI) has its own superiority in solving locking problems. And then based on the SCNI-MLS meshfree method, a unified design sensitivity analysis for the Reissner-Mindlin plate and shell with respect to size, shape and configuration design variables is presented. The optimal design examples of a shell structure are achieved by integrating the SCNI-MLS with the sequential quadratic programming method. Numerical examples verified accuracy of the design sensitivity analysis and efficiency of the design optimization proposed.