The development and property control of an intelligently magneto-sensitive (MS) and mechanically strong hydrogel practically usable for diverse biotechnological applications are challenging. In this work, we demonstrate the strategies to fabricate tough, ultrastretchable, and biocompatible MS nanocomposite hydrogels (MSNCHs) with homogeneous nanoparticle dispersion and to tune their network structure and properties for obtaining the optimal MSNCH. The MSNCHs were synthesized by the in-situ thermal polymerization of N,N-dimethylacrylamide (DMAAm), laponite nanoparticles (NPs), and Fe 3 O 4 magnetic NPs (MNPs), and their structural, thermal, swelling, and mechanical properties were examined according to the weight fraction of Fe 3 O 4 MNPs, w F . In addition, their controllable magnetorheological (MR) properties were investigated for various w F s and applied magnetic field (MF) strengths, H s. The correlation between their w F - and H -dependent structure and properties was analyzed, and the magneto-responsive performances in the air and water were also observed. Results showed that their MR properties and performance increased with increasing H , owing to the more robust filler network formed by the better-built alignment of Fe 3 O 4 MNPs, and the dominant one of the reinforcing and interruption effects of Fe 3 O 4 MNP content on the network structure determined the properties and performance of the MSNCH. The MSNCH possessing the homogenous nanoparticle dispersion and the structure, properties, and performances controlled while maintaining its high toughness, ultrastretchability, and biocompatibility holds great potential as a remote-controllable soft actuator for biomedical and pharmaceutical technologies. • Development of a tough, ultra-stretchable, biocompatible, and magneto-sensitive nanocomposite hydrogel (MSNCH). • Homogeneous dispersion of Fe 3 O 4 magnetic nanoparticles (MNPs) in the MSNCH matrix without a dispersant agent. • The control of the properties and performances of the MSNCH by tuning its network structure with MNP content and MF strength. • The reinforcing and interruption effect of MNPs on the MSNCH network structure. • MSNCH system as a promising remote-controllable soft actuator for biomedical and pharmaceutical technologies.