Summary: This article is referred to the clarification of polymerization characteristics of microgel-like network polymer precursor (NPP), closely related to the inhomogeneous polymer network formation, in the free-radical crosslinking (co)polymerization of multivinyl monomers. Firstly, the gelation in free-radical crosslinking allyl benzoate/diallyl terephthalate (DAT) copolymerization governed by Flory-Stockmayer gelation theory was explored in the presence of ethylene glycol dimethacrylate (EGDMA) as a typical multivinyl monomer. Since the copolymerizability of allyl monomer with methacrylate monomer is very poor, the crosslinking EGDMA polymerization accompanied by in situ nanogel-or microgel-like methacrylate-NPP formation was preceded. Secondly, DAT polymerization was carried out with in situ inhomogeneous network formation by a preceded crosslinking EGDMA polymerization. The structures of resulting NPPs were characterized by SEC-MALLS-viscometry. Here, the preceded in situ methacrylate-NPP formation promoted the gelation, never leading to delayed gelation. Finally, our aforementioned discussion was extended to the preparation of novel core-shell type allylic nanoparticles based on crosslinking multiallyl/multivinyl copolymerizations.