The leptonic radiative decay B → γlν is of great importance in the determination of B-meson wave functions. We compute the subleading power corrections to the form factors within the framework of PQCD approach, including the power suppressed hard kernel, the contribution from a complete set of three-particle B-meson wave functions up to twist-4 and two-particle off light-cone wave functions, the 1=mb corrections in heavy quark effective theory (HQET), and the contribution from the hadronic structure of photon. In spite of large theoretical uncertainties, the overall power suppressed contributions decreases about 50% of the leading power result. The λB dependence of the integrated branching ratio is reduced after including the subleading power contributions, thus the power corrections lead to more ambiguity in the determination of λB from B → γlν decay.