Initial state radiative correction in R measurement at BES

Three typical schemes of the initial state radiative correction in e(+) e(-) collision through single photon annihilation were reviewed, and the numerical results were calculated in the energy region of 2-5GeV. The differences of the theoretical values of radiative correction factors (1 + delta) are about 1%-2%. The uncertainty of the effective (1 + delta (obs)) is estimated to be about 2%-3%.