The simultaneous interpenetrating network samples with different gelation sequences based on plasticized polyurethane(PU) and poly(glycidyl mechacrylate)(PGMA) were prepared by changing the PU catalyst. The kinetics of network formation was monitored by FTIR. The obtained samples with different gelation sequences show opposite physical and mechanical properties. The sample with PU gelling first is transparent and brittle, while the sample with PGMA gelling first is opaque and highly elastic. The transmission electron microscopy(TEM) and dynamic mechanical analysis(DMA) methods were used to investigate the microstructures of these samples from different aspects to explain their completely different properties.