In this study we show that the plasma-initiated polymerization can be carried out at ambient temperature and pressure using the dielectric barrier discharge technology. The structure of styrene-maleic anhydride copolymer (SMA) is analyzed by Fourier transform infrared and H-1 NMR. The effects of initiation time, postpolymerization time, and polymerization temperature on conversion are also discussed. The results show that SMA exhibits a dominant alternating structure, the conversion increases with increasing initiation time, postpolymerization time, and polymerization temperature, and the plasma-initiated polymerization in this experiment is proven to follow the free radical polymerization mechanism.