Functional polymers show great potential in information storage applications. However, most of these polymer-based memory devices demonstrate limited capacity because of binary memory characteristic. Herein, three novel donor-acceptor-type bipolar conjugated copolymers containing the naphthalene benzimidazole unit as the acceptor and fluorene/carbazol as the donor were synthesized by Suzuki cross-coupling reaction. When applied in memory devices, these as-prepared polymers exhibit unique ternary resistance switch memory behaviors with high switching current ratios of 1:10(1.5):10(4), 1:10(1.7):10(5.5), and 1:10(2.3):10(3.2), respectively, low threshold voltage of -1.00 V/-1.60 V, -1.00 V/-1.45 V, and -1.45 V/-2.00 V, respectively. The retention time exceeds 10(4) s and excellent stability over 10(3) cycles. The resistance switching mechanism is well explained by the charge trap model. This work provides a new direction for the rational design and fabrication of high-performance electrical storage devices with multistage transition states.