A novel, three-dimensional material of g-C3N4/MgO was prepared by pyrolysis method. The adsorption behavior for Pb(II) onto g-C3N4/MgO was systematically investigated. The adsorption experiments confirmed that the g-C3N4/MgO exhibited remarkable adsorption performance owing to its rough morphology and abundant active sites on the surface. The maximum adsorption capacities for Pb(II) reached to 220.3, 226.2 and 235.1 mg/g at 308?K, 318?K and 328?K, respectively. The optimum adsorbent dosage was 1.0?g/L. The adsorption kinetics and isotherm could be well described by the pseudo-second-order model and Langmuir isotherm model, respectively. The adsorption process was spontaneous and endothermic.