Abstract: Taking "non-ideal column" as mechanical model of the crop stem, crop-stem deflection and the relationships between influencing factors of crop-stem lodging were analyzed under axial loading with mechanical theories. The "deflection curve" for stems of three wheat cultivars under different axial loadings were measured with a simple equipment, then relative testing data was analyzed scientifically. The results indicated that shape changing of crop-stem deflection curve was caused by many factors and coordinates of "deflection curve" had the obvious physical meaning, was easy to measure and simple to operate. The coordinates of "deflection curve" could be used to evaluate the lodging resistance. In this article, its reasonability to evaluate lodging resistance was proved both theoretically and experimentally. This research further provides references for crop lodging resistance research and related agricultural machine designing.