The last unknown neutrino mixing angle has been successfully measured by the Daya Bay, RENO and Double Chooz experiments. The used oscillation probability formula is based on the plane-wave model. A wave-packet model is necessary for a self-consistent description of neutrino oscillations. The oscillation probability formula in the wave-packet model describes effects missing in the plane-wave approximation, such as delocalization, decoherence and dispersion which all depend on a single unknown parameter σp - momentum dispersion of the neutrino wave-packet. The survival probability formula in the wave-packet model was used to fit the Daya Bay data. The high-statistics data set of reactor ν ¯ e interactions in the Daya Bay experiment allows us to study the neutrino oscillation in the wave-packet model and provide the first experimental constraint of σp. Some results of our study are reported in this paper.