Toehold-mediated strand displacement (TMSD) reaction is a widely used programming language in DNA nanotechnology, but its performance is significantly limited by slow kinetics, especially for low-concentration reactants. Herein, we report on polyquaternium-2 (PQ2) as an effective and efficient accelerator of TMSD reaction. We show that PQ2 could drastically increase the reaction constant of 1-nt TMSD by 10