CdS and ZnS quantum dots were obtained via a modified gel crystal growth method using hydrogel (HR) as a kind of gel and a special substrate, which effectively suppressed the agglomeration of CdS and ZnS nanoparticles in the growth process via using chemical adsorption effect and utilizing the feature of gel crystal growth method (the sites of nuclei, growth and minimizing precipitation for the crystals were restricted spatially in the gel). The structural, growth mechanism and photocatalytic H-2 evolution properties of these MS(M= Cd, Zn)/HR were investigated. The MS/HR composites exhibited high rates of H-2 evolution compared to those of bulk MS, benefited to the synergistic effect of quantum dots and HR. The quantum dots extend the band gap and provide abundant catalytically-active sites and HR was used as a miniature hydrogen production reactor due to the large volumes of water in its swollen structure derived from its super H2O adsorption capacity, which efficiently avoided the agglomeration of MS quantum dots during the photocatalytic hydrogen evolution process. This work may provide an excellent approach for the preparation of quantum dots and miniature hydrogen production reactor shows a potential application in water splitting.