Abstract: A tungsten and molybdenum mixed heteropoly acid salt catalyst (Na₄SiMoW₁₂O₄₀·xH₂O) is prepared by using Na₂WO₄·2H₂O and Na₂MoO₄·2H₂O as raw materials through the combination of nitric acid acidification and ether extraction technique. The resulting catalyst is characterized by X-ray fluorescence spectrometer (XRF) for the investigation of its elemental composition. The infrared spectroscopy (FTIR) is used to analyze its functional group structure. The thermogravimetric analysis (TGA) is used to study its thermal stability. The catalytic activity and stability of the tungsten and molybdenum mixed heteropoly acid salt catalyst are studied during the process of esterification reaction of butanol and acetic acid. The key reaction parameters that influence the yield of n-butyl acetate are optimized by employing an orthogonal experiment L₉(3)⁴, including the mass loading of catalyst, reaction time and reaction temperature, as well as the molar ratio of butanol to acetic acid. Results show that esterification reaction effect of 93.24 wt% is obtained when the reaction time is 120 minutes, reaction temperature is 90 ℃ and catalyst loading is 0.4 g with the molar ratio of butanol to acetic acid of being 2:1.