By using the definition of topological pressure for subadditive potentials, we introduce a new definition of measure-theoretic pressure for ergodic measures of subadditive potentials on a compact metric space. Under some assumption, we show that this definition has a similar formalism to the definition of measure-theoretic pressure for ergodic measures of additive potentials on a compact metric space. As an application, assume that the subadditive potential is Hölder continuous, then for an expansive homeomorphism with the specification property, we study the relationship between the measure-theoretic pressure and the periodic points.