An enzyme-free and label-free fluorescent DNA aptasensor was constructed with computer assistance based on thermodynamic deviation driving interchain reactions. In this work, in the presence of target acetamiprid, the released trigger strand C-apt could open hairpin Hp1, which in turn triggered the strand displacement reaction and catalyzed the self-assembly of hairpins Hp1 and Hp2, so that the guanine base rich stem in Hp2 was opened. In the presence of K+ and NMM, the G-rich moiety could form a G-quadruplex and emit strong fluorescence at a specific excitation wavelength. The proposed strategy enables sensitive detection of acetamiprid at concentrations as low as 54.3 pM. Most importantly, computer-assisted analysis of the thermodynamic properties of nucleic acid strands and simulation of the reaction process and conditions of the proposed model before conducting biological experiments theoretically proves this strategy feasible and may simplify subsequent biological experiments. In addition, basic molecular logic gates, including OR and AND, were constructed based on this detection principle, and simulation tests and biological experiments were performed. The final results show that this strategy can not only have some applications in the field of food safety and environmental monitoring, but also provide a certain way for the development of molecular logic computing.