The specific heat C(T) of BaFe2As2 single crystal, Ba0.7La0.3Fe2As2 and Ba0.5K0.5Fe2As2 polycrystals were measured. For undoped BaFe2As2 single crystal, a very sharp specific heat peak, 3 times higher than that in previous polycrystalline sample, was observed at 136 K. This is attributed to the structural and antiferromagnetic transitions occurring at the same temperature. C(T) of non-superconducting electron-doped Ba0.7La0.3Fe2As2 also shows a small peak at 120 K, indicating a weak structural/antiferromagnetic transition. For the hole-doped Ba0.5K0.5Fe2As2, a clear specific heat peak of C/T was observed near the superconducting transition temperature Tc = 36 K. The electronic specific heat coefficient gamma of these compounds were obtained by fitting the low temperature data.