Organic ternary memory devices show higher data storage density than common inorganic binary memory, however, facing the challenge of the low ON/OFF current ratio and high threshold voltage hinders their application. Herein, a conjugated polymer, poly[2,7-(9,9-dioctyl)-fluorene-alt-12 H-benz[5,6]-isoindole[2,1-a] benzimidazole-12-one] (PFBIM), was synthesized and applied to fabricate memristors by spin coating. The PFBIM-based memristors showed unique ternary memory behavior, but their ON/OFF ratio is just 9.6 × 103 and the threshold voltage is − 1.35 V. To improve memory performance, the strategy of polymer film blends Pt NPs was implemented. Impressively, enhanced performance was achieved when the PFBIM-based memristor incorporated 5% Pt NPs, the ON/OFF ratio increased to 1.37 × 105 and the threshold voltage decreased to − 0.65 V. The ternary switching mechanism and the role of Pt NPs on enhanced memristor performance were studied. This work may provide useful information to ameliorate performance and promote the further advance of ternary memory devices.