Hydrogen plasma plays an important role in various situations such as nuclear fusion and plasma processes. In this study, optical emission spectroscopic measurement was conducted for the Fulcher-α band of H2 molecule radiated from the microwave discharge hydrogen plasma. Conventional numerical procedure was found to be insufficient to calculate the Fulcher-α band in terms of wavelength. It was also found that the common shift of the excited energy of the rotational levels could justifiably fit the theoretical spectrum with the one observed experimentally for vibrational levels v’ = 0 – 3. By the best fitting procedure of the both spectra, the modification of the rotational energy constant Bv of H2 a 3Σg+ state is proposed as a quadratic function of the vibrational quantum number.