Abstract: The study on the biomechanical properties of stalk crops can offer design parameters of machines related to the mechanized production and agro-product processing, and evaluate different biomechanical performance indexes on stalk crop breeding. In this paper, the bending experiments were performed on different wheat varieties(high stalk, medium stalk and short stalk) in different growth periods, two different types of corn stalks at the filling stage, two different types of broomcorn stalks at the filling stage, and two different varieties of bean stalks at the podding-seedfilling stage. Based on the experiment data, the biomechanical performance indexes for stem-lodging resistance were studied and analyzed correlatively. The relationship between the indexes in different periods (such as Young's modulus, bending strength, cross sectional moment of inertia, and bending rigidity) and lodging resistance was explored by the analysis of the grey relational degree. Taking wheat stalk as an example, the weight coefficient on the indexes had been calculated and tested. It was found that, in the biomechanical performance indexes of different varieties, bending strength, cross sectional moment of inertia, and Young's modulus were highly correlated with lodging index, while bending rigidity was less correlated with lodging index.