Phase compositions, microstructures and microwave dielectric properties of the MgTiO3 and Mgn+1TinO3n+1 (1 <= n <= 7, 50) specimens prepared via the conventional solid-state reaction route were investigated. X-ray patterns revealed that a certain amount of the Mgn+1TinO3n+1 phases were detected in the specimens with n = 2-5. Additionally, a visualization of the MgTiO3, Mg2TiO4 unit cell and the considered Mg-Ti-O layered supercells were described, and the layered rhombohedral Mg-Ti-O phases were supposed to make the crystal structure more stable. Both EDS and Raman spectrum analysis results proved that the Mgn+1TinO3n+1 (2 <= n <= 5) phases indeed existed in the present systems. Besides, the Qxf value was extremely sensitive to the analogical layered phases content and compactness. A relative higher content of Mgn+1TinO3n+1 (2 <= n <= 5) phases and a well-developed microstructure could cause an extremely low dielectric loss in these ceramic systems. Moreover, some very high Qxf values (>300,000 GHz) could also be achieved for the Mgn+1TinO3n+1 (n = 6, 7) systems as well. Thus, the Mgn+1TinO3n+1 ceramic systems were expected to substitute for conventional MgTiO3 or Mg2TiO4 systems to form some novel microwave dielectric materials with the ultralow dielectric loss. (C) 2017 Elsevier B.V. All rights reserved.