Effect of pH value and calcination temperature on the crystalline properties of MgO nanosheets was investigated via liquid phase method in alcohol-water system with Mg(NO3)2?6H2O as magnesium, PEG-2000 as surfactant and NH3?H2O as precipitant. The crystal phase composition, morphology and pore structure of MgO nanosheets were characterized by XRD, SEM and BET. The results indicate that pH value and calcination temperature have no effect on the phase composition of MgO nanosheets, but posed significant impact on the micro- morphology and specific surface area of MgO nanosheets. Lower pH value and calcination temperature, or higher pH value and calcination temperature cause irregular shape and different degree of agglomeration of samples, with smaller specific surface area. The products has regular shape and good dispersibility under the condition of pH=10 and calcination temperature of 500 ℃, specific surface area of 145.42 m2?g-1, pore volume of 0.67 cm3?g-1 and average pore diameter of 18.56 nm.