The structures and energies of ［001］ symmetrical tilt grain boundaries (STGB) in BCC metal Li have been simulated in atomic level by using modified analytical embedded atom method (MAEAM). The energies of two rigid-body crystals joined together directly are abnormally high due to very short distance between atoms near grain boundary (GB) plane. For each of 27 GB planes, the relative slide between grains could result in a significant decrease in GB energy and a minimum value could be obtained at specific translation distance, which increases with increasing inverse density of coincidence-site Σ, but decreases with increasing interplanar spacing da. From minimization of GB energy, the three lowest minimum-energies are corresponding to (310)、 (530) and (510) GB planes successively, which should be preferable in planes.

Lithium； symmetrical tilt grain boundary (STGB); modified analytical embedded atom method (MAEAM); grain boundary (GB) energy