Based on the theory of material thermodynamic surface tension, a research has been conducted on the relationship between vacancy formation energy and elastic deformation parameter of metal materials-Young modulus so as to establish an internal correlation mechanism between microscopic vacancy defect and macroscopic mechanical properties. According to the research results, vacancy formation energy and Young modulus are the external reflection of the binding energy with a regular linear relationship between them, and the proportionality coefficient ranges from 0.005 to 0.008. The mechanism provides a reference for the mutual prediction of macroscopic mechanical properties and microscopic vacancy defect in metallic materials.