Compliant Mechanisms (CMs) have presented their inherently advantageous properties since the nature of CMs is to utilize elastic deformation of the built-in elementary flexible members to transfer motion, force and energy. To predict the performances of CMs and optimize their designs, modeling CMs turns out to be a major concern in this field, particularly, such as highprecision flexure-based CMs. Reported in the literature, the famous Beam Constraint Model (BCM) expressed in Cartesian coordinate system serves as an effective tool to model the deflection of flexures. Inspired by BCM, in this paper, we take one step further to propose a Bodyframe Beam Constraint Model (BBCM) to handle buckling and intermediate-range deflections under typical beam-end loading conditions. Numerical and analytical analysis also proves that BBCM can also provide reliable accuracy in complex loading conditions and complex beam geometries within small-to-intermediate-range deflections and may accurately characterize large deflections under some specific loading conditions as well.