Physical properties are closely associated with the variation of electronic states. This work provides a theoretical analysis of (pi) and Sigma (sigma) electron redistribution in boron-doped graphene by density functional theory (DFT). An energy gradient appears for pi electrons which homogeneously distributed in pristine graphene evolving into a distribution with energies gradually decreasing from the substitutional boron to further carbon atoms. The introduction of boron not only affects the distribution of pi electrons but also sigma electrons. An increasing boron concentration makes sigma electrons changed from localized states to delocalized states, which is attributed to the impurity bands caused by the formation of B-C and B-B bonds. An opposite charge transfer direction for pi and sigma electrons (from C to B and B to C, respectively) is observed which further confirms that the substitutional boron in graphene acts as the pi acceptor and sigma donor. A better understanding of redistribution of electrons in graphene is either as the prerequisite to explore the root cause of change in microscopic properties or as a foundation for further application of dopants doped graphene or carbon materials.