A three-dimensional convective cloud model with a hail-bin microphysics scheme and a hail growth model were used to further investigate the growth mechanism of large hail in supercell storms. The observed supercell features such as quasi-steady mesocyclone, a pronounced bounded weak echo region and a forward overhang were reproduced well by the simulation. During the storm developing stage, hail embryos were produced mainly by the freezing process of raindrops and occurred at the top of the main updraft region and the mid- to upper-portion of the storm from the northwest flank of the main updraft region. Approximately 7%-8% of hail embryos forming at the developing stage continued to grow into hail larger than 10 mm in diameter; only 1% of hail embryos ultimately achieved diameters of 20 mm. Most of the largest hailstones grew from millimeter-size embryos that originated in the upper-level region around the north flank of the updraft and thereafter entered the main updraft cyclonically and grew into large hailstones in a single up-down path. Other embryos originated in the upper-level region of the northwest flank around the main updraft and grew into large hailstones in a down-up-down path along the updraft edge cyclonically. These results suggest that there are two growth paths for large hailstones in supercell storms.