The biomedical and industrial application of hydrogels are strongly limited by their poor mechanical properties. In this paper, non-aggregated Ca(OH) nano-spherulites (CNS) with diameters <5 nm is synthesized and used to reinforce polyacrylamide (PAM) hydrogel. The CNS/PAM hydrogel obtained possesses super stretchable property, high toughness, and strength with low CNS concentration. Molecular dynamics (MD) is employed to study the reinforced mechanism of the CNS to promote the further application of CNS in the field of hydrogel. In the network structure of hydrogel, the interaction between CNS and PAM contributes to the formation of cross-linked nodes around CNS, in which PAM chains play roles in reinforcement and connection, respectively. Furthermore, the introduction of CNS leads to more chemical bonds and cross-linked nodes formed in the structure, which significantly improves the tensile strength and elastic modulus of the hydrogel, but decreases the stretchable properties to some extent. Interestingly, CNS also has a beneficial side to improve the stretchable properties via the division into relatively small CNSs under high stress. Both experimental results and theoretical simulations deepen the understanding of nanocomposite hydrogels and can promote the application of CNS to other polymeric hydrogel for property enhancement.