Thermodynamic analysis of single-step synthesis of dimethyl ether (DME) from syngas over a bi-functional catalyst (BFC) in a slurry bed reactor has been investigated as a function of temperature (200-240 degrees C), pressure (20-50 bar), and composition feed ratio (H-2/CO: 1-2). The BFC was prepared by physical mixing of CuO/ZnO/Al2O3 as a methanol synthesis catalyst and H-ZSM-5 as a methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H-2, methanol dehydration to DME and water-gas shift reaction were chosen as the independent reactions. The equilibrium thermodynamic analysis includes a theoretical model predicting the behaviour and a comparison to experimental results. Theoretical model calculations of thermodynamic equilibrium constants of the reactions and equilibrium composition of all components at different reaction temperature, pressure, and H-2/CO ratio in feed are in good accordance with experimental values.