Using a silicone demulsifier is an efficient approach in the treatment of environmental pollution caused by aged oil. A new type of silicone demulsifier was prepared in this work by following a two-step synthesis method based on SP169 (octadecanol block polyether) and AE16 (monoamine aliphatic alkyl block polyether). Reaction conditions, such as reaction time, temperature, etc., were optimized for the synthesis of poly(ether ester) intermediates and silicone demulsifier. Both the proton nuclear magnetic resonance and infrared spectra confirmed the successful preparation of poly(ether ester) intermediates from acrylic acid based on the presence of the C=C and C=O bonds provided, indicating the successful modification of the silicone demulsifier by the polysiloxane and poly(ether ester) intermediates. The thermal degradation interval of the silicone demulsifier is 325-390 degrees C according to thermogravimetric analysis. In addition, the diffusion and adsorption of the silicone demulsifier, which were measured by a quartz crystal microbalance with dissipation, indicated that the silicone demulsifier forms a compact and uniform adsorbed layer, which contributed to the demulsification. The dehydration rate was 86.87% when the poly(ether ester) ratio, silicone demulsifier dosage, demulsification temperature, and time were 2:1, 150 mg/L, 65 degrees C, and 1.5 h, respectively, during the demulsification tests. The silicone demulsifier has great potential application in oil/water separations of aged oil.