In this article, semi-interpenetrating polymer network (Semi-IPNs) based on nitrile rubber (NBR) and poly(methyl methacrylate-co-butyl acrylate) (P(MMA-BA)) were synthesized. The structure and damping properties of the prepared Semi-IPNs blends were characterized and by fourier transform infrared spectrum (FTIR), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and tensile mechanical properties. The results showed that interpenetrating network based on P(MMA-BA) and NBR was successfully obtained, which showed the improved thermal stability compared to NBR/P(MMA-BA)-based two-roll mill blends. Furthermore, Semi-IPNs showed significantly better the dynamic mechanical properties than that of the two-roll mill system. With the increasing feed ratio of BA and MMA during the preparation of Semi-IPNs, the loss peak position for P(MMA-BA) in NBR/PMMA IPNs shifted to a lower temperature from 20°C to −17°C, and when NBR in Semi-IPNs was accounted for 40 wt %, the dynamic mechanical thermal analysis showed that much more advanced damping material with wider temperature range (−30°C < T < 80°C) as tan δ > 0.45 can be achieved. Therefore, it was expected as a promising way to obtain the excellent damping materials with good oil-resisted properties according the Semi-IPNs system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40217.