X-ray absorption fine structure (XAFS) was used to investigate the local structures around Ga atoms in the hexagonal nanocryst alline and crystalline GaN under 78K and 300K. For the first nearest-neighbor coordination of Ga-N, the average bond length R, coordination N, thermal disorder σ_T and structural disorder σ_S of nanocrystalline GaN ar e similar to those of crystalline GaN, which are 0.194nm, 4.0,0.0052nm and 0.000 7nm, respectively. When the temperature is elevated from 78K to 300K, the σ_T in GaN samples increases by lower than 0.0005nm. It indicates that the Ga- N covalent bond is much stronger, and is nearly independent of temperature and c rystalline state. For the second nearest-neighbor Ga-Ga coordination, the R values of the samples are about 0.318nm; the σ_S(0.0057nm) of nanocryst alline GaN is 0.0047nm larger than that of crystalline GaN(0.001nm); the σ_T of Ga-Ga coordination in nanocrystalline GaN are 0.0053nm, 0.0085nm for the temperature of 78K and 300K, respectively. This shows that the σ_T of Ga- Ga coordination is greatly affected by the temperature. The major difference of local structure around Ga atoms between nanocrystalline GaN and crystalline GaN is shown by the relatively large σ_S of the Ga-Ga second nearest-neighbo r shell in nanocrystalline GaN. The reason may be explained by that there exist larger defects and unsaturated surface atoms in nanocrystalline GaN.