Abstract: The homopolymer of N, N-dimethylacrylamide (PDMA) and the copolymer of N, N-dimethylacrylamide and acrylamide (P(DMA-co-AM)) were synthesized by aqueous solution polymerization. The effects of intrinsic viscosity, the molar ratio of AM to DMA, temperature and shear rate on the rheological behaviors of polymer solution were studied, and used as a separation medium for DNA fragments analysis using capillary electrophoresis. The study of rheological behaviors show that with increasing the AM content the intrinsic viscosity of P(DMA-co-AM) increased, and the viscosity of the DNA separation solution formed by the polymer in the buffer solution increased. When the temperature increased from 25 ℃ to 60 ℃ at a constant shear rate, the viscosity of PDMA separation solution with higher molecular weight decreased by 57.0%, while the viscosity of P(DMA-co-AM) solution with higher molecular weight decreased by about 50.8%. Compared with the PDMA solution, P(DMA-co-AM) solution could better resist the environmental temperature change. The results of DNA fragment analysis show that with increasing the AM content, the P(DMA-co-AM) solution with higher molecular weight obtained a higher resolution on the separation of big fragments of DNA and better reproducibility compared with the P(DMA-co-AM) solution with lower molecular weight.