In this study, a series of Y3Al5O12:Sm3+ luminescent materials with different Sm doping were successfully synthesized by the sol-gel combustion method, and characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectrum to investigate the relationships among structure, luminescent properties and Sm3+ concentration, and the mechanism of self concentration quenching of Sm3+. It is found that the Sm3+ concentration has no effect on the crystal structure with the strongest excitation peak of 405 nm, corresponding to the 6H5/2→4F7/2 transition of Sm3+. At 405 nm excitation, the Y3Al5O12:Sm3+ gives a red luminescence centered at about 617 nm (4G5/2→6H7/2). The suitable doping-concentration of Sm3+ in Y3Al5O12 is 3 mol%, and the quenching mechanism is the cross relaxation (4G5/2+6H5/2→6F9/2+6F9/2) caused by the interaction of electric quadrupoles between Sm3+ ions