Abstract: In this paper, water-based silver platinum alloy nanofluids were prepared by using ascorbic acid (C₆ H₈ O₆) as reducing agent by reducing platinic acid (H₂ Pt (OH)₆) and silver acetate (CH₃COOAg). The effects of flow rate, temperature and molar ratio of surfactant (PVP) on the viscosity, stability and thermal conductivity of nanofluid were studied. The experimental results show that the stability and thermal conductivity of the nanofluid are the best when the molar ratio of PVP is 5, the flow rate is 0. 5 mL/min and the reaction temperature is 50 ℃. When the fluid temperature is 60 ℃, the thermal conductivity increases by 16. 92% compared with the base fluid. With the increase of PVP molar ratio, reaction temperature and flow rate, the thermal conductivity of nanofluid firstly increased and then decreased. The viscosity of nanofluid increases with the increase of surfactant concentration, and decreases first and then increases with the increase of reaction temperature and flow rate. When the reaction temperature is 50 ℃, the viscosity of the nanofluid is the lowest, and the viscosity of the nanofluid is increased by 36. 51% compared with that of deionized water.