The X-ray powder diffraction, properties of normal state and superconducting state (especially carrier concentration) measurements were carried out for the high quality and single phase polycrystal Bi2Sr2CaCu2O8+δ samples annealed in low vacuum or H2 atmosphere at various temperatures. The results reveal that the oxygen atoms escape for Bi2Sr2CaCu2O8+δ samples annealed in H2 atmosphere is devided into two steps. First, the extra oxygen atoms residing between the Bi-O layers escape, and the carrier concentration of samples decreases, the superconducting transition temperature Tc of samples is modulated. Second, the oxygen atoms in the CuO2 planes are removed, and the oxygen vacancies, which induce the short range 2D-AFM order of Cu2+ to decrease, emerge in the CuO2 planes, We suggest that the variation of Tc led by hydrogen absorption in the Bi2Sr2CaCu2O8+δ superconductor might be mainly brought on by the oxygen content variation in the course of absorbing hydrogen, rather than by the electron dopping effect of hydrogen atoms.