In order to improve the numerical calculation accuracy during mesh deformation, based on the concept of asymmetric finite elements, a US-FE-LSPIM QUADRILATERAL ELEMENT is proposed. This unit is composed of two different sets of shape functions, namely, the traditional set of four-node isoparameter functions and the set of FE-LSPIM quadrilateral element shape functions as test functions and test functions, respectively. It can easily apply displacement boundary conditions over the entire length. By studying the performance of the quadrilateral element in the two-dimensional free vibration of the cantilever beam, it is shown that the unit has high calculation accuracy. And under the deformed mesh, the result of this element is better than that of the QUAD4 element, which is insensitive to mesh deformation.