The recovery of heavy oil is challenging due to its high viscosity and low mobility. Emulsifying heavy oil into stable heavy oil-in-water emulsions is an effective strategy to improve heavy oil mobility and enhance oil recovery. However，on space-constrained offshore platforms，these emulsions must be rapidly demulsified after production，so the development of stimuli-responsive demulsification technology has become a research priority. In this study，a responsive EO-PO type pseudo-gemini surfactant，di （C_18:1E₅） -P_2-3，was synthesized via an acid-base neutralization reaction and subsequently compounded with SiO₂ nanoparticles to formulate a switchable active nanofluid. The thermal and salinity tolerance of di （C_18:1E₅） -P_2-3，alongside the emulsification viscosity reduction performance of the active nanofluid for heavy oil，were systematically investigated. Furthermore，the interfacial stabilization mechanism and the stimuli-responsive demulsification performance of the heavy oil emulsion were thoroughly explored. The results demonstrated that the surfactant exhibited excellent thermal and salt tolerance，making it suitable for high-temperature and high-salinity reservoirs. The active nanofluid，formulated by combining the surfactant with nano-SiO₂，efficiently stabilized heavy oil-in-water emulsions，achieving a water separation rate as low as 5 . 5 % after 30 minutes of standing and a viscosity reduction rate exceeding 95 %. The exceptional emulsion stability stemmed from the synergistic adsorption of di （C_18:1E₅） -P_2-3，SiO₂ nanoparticles，and asphaltenes at the oil-water interface，which collectively formed a dense interfacial film that effectively inhibited droplet coalescence. More importantly，the heavy oil emulsion exhibited excellent stimuli-responsive demulsification performance. Upon bubbling CO₂，the pseudo-gemini surfactant dissociated，resulting in a water separation rate approaching 100 % within only 5 minutes of standing. This work enables simultaneous achievement of enhanced heavy oil recovery via subsurface emulsification and rapid demulsification of produced emulsions，providing an innovative and feasible technical pathway for the green and intelligent development of offshore heavy oil.