The magnetic properties and electronic structure of (LaMnO3)n/(SrTiO3)m superlattices are investigated using the full-scale first principles density functional theory calculations in order to reveal the magnetic ground state and transport of the thin LaMnO3 layers sandwiched by relatively thick SrTiO3 layers. The LaMnO3 layer in the superlattices favors the ferromagnetic metallic state rather than the A-type antiferromagnetic insulator. It is revealed that the strain and asymmetric chemical environment may induce tiny magnetic moment to Ti ions of the SrTiO3 layer near the interface. The possible mechanism for these phenomena is discussed.