Perovskite quantum dots (PQDs) have been widely studied due to the outstanding light emission properties including high quantum efficiency, narrow linewidths and electron transport properties. However, poor stability limits their implication in optical devices, especially working at ambient conditions in the presence of moisture that rapidly attenuate their performance. In this work, PQDs were loaded in nanosized EMT zeolite crystals synthesized from template-free precursor systems resulting in a composite EMT-CsPbBr 3. We found and studied for the first time that, in the pores of the zeolites, a small amount of water molecules can promote the crystallization of perovskite nanocrystals. The energy and bond length of perovskite CsPbBr 3 confined in the cages of EMT zeolite were calculated in the presence of water molecules, corresponding to the effect of humidity. Crucially, the pore structure of EMT molecular sieve provides an important research model. The great stability and reliability of the EMT-CsPbBr 3 as humidity sensor is presented. The luminous intensity efficiency of the EMT-CsPbBr 3 composite was maintained at nearly 90% after continuous usage for 6 months. Both the theoretical and experimental results show that a trace amount of water enhances the luminescence of perovskite stabilized in the hydrophilic EMT zeolite.