Using the first-principles method, we investigate the hydrogen adsorption on the polarAlO2 surfaceof LaAlO3–SrTiO3 heterostructures with an n-type interface. It is found that the H atom ismost stable when bound at the surface O atom. The adsorption energyfor a given H density is lowered (i.e., stronger binding) with increasingLaAlO3 thickness. The adsorbed H atom donates electrons to the conduction band ofSrTiO3, which results in the metallic conductivity ofSrTiO3. The chargetransfer from H to SrTiO3 significantly alters the electrostatic boundary condition and the Coulombic divergence insideLaAlO3 completely disappears when one H atom is adsorbed every (2 × 1) surface unit cell. Our results also indicate thatH2 orH2O molecules exothermically dissociate and adsorb on the surface when theLaAlO3 layer is thicker than certain critical values, suggesting that theH adsorption may play a role in the conducting properties ofLaAlO3–SrTiO3 heterostructures observed in experiment.