The influence of absorption gratings on energy transfer of photorefractive two-wave mixing in Bi_(12)TiO_(20)is investigated. It is based on the dependence of the absorption coefficient in Bi_(12)TiO_(20)on the incident beam intensity. The expressions of energy transfer for two-wave mixing in Bi_(12)TiO_(20)are derived under certain condition and compared with the experimental results. The gains of the pure absorption gratings are meaured omd the results given.