The BiOX (X=Cl, Br and I) single crystal was prepared by the vapor gas transport reaction method in closed volume. The specific heat measurements in the zero and 8 T magnetic field carried out in the temperature range 2–300 K for BiOX single crystals using the PPMS. At temperatures below 4,5 K, the specific heat of BiOX shows a classical behaviour with a T<sup>3</sup> temperature variation. Between 13 K (BiOCl, BiOBr) and 15 K (BiOI), deviations from the T<sup>3</sup> law appear and are explained by means of four Einstein oscillators. The values of Debye temperature θD are 205K, 168K and 146K for BiOCl, BiOBr, and BiOI, respectively. The values of entropy S=101.7, 108.6 and 119.5 J/moleK for BiOCl, BiOBr and BiOI, respectively.