In this Article, we report a systematic research on a hydrogel with dual networks of 104 times difference in mesh sizes. The structure was developed by polymerizing a cationic monomer N-[3-(N,N-dimethylamino)propyl] acrylamide methyl chloride quarternary (DMAPAA-Q) in the presence of a small amount of semirigid polyanion, poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT). During the polymerization, polyion complexes were formed, which caused viscoelastic phase separation (VPS) due to the self-assembly of the semirigid polyion complexes, whereupon the dynamic coupling of phase separation and gelation is crucial for the structure formation. When PBDT was above its overlap concentration (CPBDT > C*), a critical concentration of cationic monomer, CQ ≈ 1.5 M, was observed, below which VPS occurred and turbid hydrogels with the dual network structure were formed, whereas above which, a transparent, anisotropic hydrogel was formed. It has been elucidated that the critical effect of CQ on the VPS process is through the ionic strength mechanism. That is, the abundant unreacted cationic monomer at high CQ behaves as a simple salt that screens the electrostatic interaction between the polycation and PBDT and therefore suppresses the occurrence of the phase separation. Furthermore, we investigated the effects of reaction kinetics on the VPS and the microstructure of gels by changing the concentrations of photoinitiator and chemical cross-linker. The dual network gels possess controllable turbidity degrees and mesh sizes corresponding to different quench depths of the phase separation. On the basis of these results, as well as in situ observation of the structure formation during the polymerization, we proposed a detailed mechanism for the formation of dual networks and the anisotropic hydrogels.