In this article, ionic liquid-type imidazole gemini surfactants with different spacer length ([C14-n-C14im]Br2, n = 2, 4, 6) were synthesized and 3D nanostructures were constructed by using a novel Preyssler-type POM (K12.5Na1.5[NaP5W30O110]∙15H2O, abbreviated as P5W30) and [C14-n-C14im]Br2 through the ionic self-assembly (ISA) strategy. Hybrid nanostructures were fully characterized by various characterization methods, such as transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray small-angle scattering, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). By changing the spacer length of [C14-n-C14im]Br2, the rigidity and space volume of the gemini surfactants can change, which can affect the behavior of [C14-n-C14im]Br2/P5W30, such as the size of the nanostructures, the behavior of thermotropic liquid crystals, d spacing of SAXS, spatial displacement and decomposition temperature. In addition, the calcined [C14-6-C14im]Br2/P5W30 nanostructures exhibit excellent degradation efficiency for methyl orange dyes (MO), which maybe have outstanding application prospects for wastewater treatment. The nanostructure formed by self-assembly not only realizes heterogeneous catalysis, but also solves the problem of water solubility of P5W30 which was easy to recycle. Moreover, the active sites of nanostructures formed by ion self-assembly increase, and the degradation rate was nearly 3 times higher than that of pure P5W30. Our work confirmed that POM and gemini surfactants can construct functional nanostructures through ISA strategy, which can be the perfect candidate for photocatalysis and biomedical.