In the present paper, strain in GaN epitaxial layer grown by hydride vapor phase epitaxy (HVPE) was investigated by means of high-resolution X-ray diffraction (HRXRD), Raman spectra and photoluminescence (PL) measurements. Both the biaxial in-plane and out-of-plane strains (of the order of -10(-4) and 10(-4), respectively) and the hydrostatic strain component (of the order of -10(-5)) were extracted from HRXRD measurements. These values agreed well with the ones computed from the blue-shift of E2 Raman mode and the near-band-edge PL peak. The results showed that strains in GaN layer were superposed by the biaxial strain and hydrostatic strain.