An improved localized molecular-orbital assembler (LMOA) approach is developed for ground-state Hartree-Fock (HF) calculations of general large systems. Different from the original LMOA approach (W. Li and S. Li, J. Chem. Phys. 122 (2005) 194109), each subsystem is placed into background point charges, which are used to model the electrostatic and polarization interactions between a given subsystem and all other atoms (beyond this subsystem). For a wide range of neutral and charged systems, the present LMOA-HF approach is demonstrated to offer a significant improvement on the original LMOA-HF approach, providing satisfactory descriptions on their total HF energies and energy gradients. (C) 2012 Elsevier B.V. All rights reserved.