One of the major issues confronting the crude oil extraction process is the formation of various types of petroleum emulsions, particularly, water in crude oil emulsions (W/O) due to the presence of water and other natural products in crude oil. Natural product molecules help keep the water/oil interface stable and prevent water droplets from coalescing. In this paper, a polymeric Gemini surfactant was prepared as a demulsifier by condensation polymerization between phthalic anhydride and glycerol. In the laboratory, the physical characterizations of Nasiriya crude oil like water content, specific gravity, sulfur content, density, and viscosity were determined. The viscosity average molecular weight of the polymeric demulsifier was (2653 g/mol) when the constants (k=0.0002 and α=0.76). The active groups of a synthetic polymer were identified using FT-IR spectra. The authors made a Critical Micelle Concentration (CMC) of the demulsifier. The conductivity of the demulsifier was linearly proportional to the concentration of the demulsifier. The hydrophilic– lipophilic balance (HLB) of polymeric demulsifier was 11.3, which can treat Oil in Water (O/W) emulsions. The different acidity measurements of the polymeric demulsifier were shown to be generally acidic. The best result of water separation from crude oil was at conditions (30 minutes, 100 ppm, PH = 3.9, and the best value of separation efficiency of the demulsifier was 60%.