Two-dimensional Ruddlesden-Popper perovskites L2PbI4 (L = alkylammonium cation) (RPPs) have attracted significant attention due to their unique excitonic characteristics. However, their ultrafast reaction dynamics exacerbates the structural distortion of the inorganic framework, leading to severe deterioration in photoluminescence. Here, we propose a water-oil interfacial synthesis approach to achieve controlled growth of the RPPs nanosheets. By segregating Pb and I precursors in two immiscible solvents, the nucleation and growth of RPPs are prolonged to the minute level. L2PbI4 nanosheets terminated with various alkylammonium are synthesized, and the factors influencing the growth kinetics of RPPs nanosheets are investigated. The resulting (PEA)2PbI4 nanosheets exhibit a 3.6-time enhancement in quantum efficiency and 3.2-time improvement photostability compared to those synthesized using the classical recrystallization method. A white light-emitting diode based on (HDA)2PbI4 nanosheets is fabricated, achieving a color gamut of 119.7% of the NTSC display standards. This innovative approach offers a new method for the controlled growth of 2D RPPs with improved optical quality and stability.