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LiFePO4 is a promising candidate for the cathode materials due to its attractive advantages,hence,deep and thorough studies are essential.In this paper,we propose a method to modify the valences of the ions based on the Mulliken overlap populations,and then calculate the chemical bond properties and isomer shift of LiFePO4.The calculated isomer shift is in good agreement with the experimental one,supporting the correctness of our theory and method.In addition,the results of chemical bond properties indicate that the distorted structure of FeO6 may be the reason for the difference in the polarization and covalency among the Fe-0 bonds,and finally bring variation of bond properties and isomer shift.The semiempirical model can be employed to other series of complex compounds and provide comprehensive information from chemical bond viewpoint for further studies,such as the influence of change in valence and crystal structure on the macroscopic characteristics and so as to predict some properties for new compounds.