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 acrylamide to N, N-dimethylacrylamide, 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.