Single element mesh shape evaluate index of ANSYS and SAP2000 is analyzed and summarized in the present paper.Based on this indexes, a new index is proposed. Benefit from the new index, not only single element mesh but also mesh compose of more elements can be evaluated. A cantilever beam problem is meshed by different shape and procedure programmed by C++ language is used to calculate this index of the mesh, after compared the solution with exact one, a conclusion can be draw that there is a strong correlation between the index value and the precision of solution. Multilayer and high-rise buildings mesh is also evaluated, the results show the index is still efficient and reliable.