A series of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12 (n=0,1,2) were prepared in the BaO-La2O3-TiO2-Nb2O5 system by high temperature solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction,scanning electron microscope,and microwave dielectric properties measurements. These samples were identified as single phase and adopted A4B3O12-type cation-deficient hexagonal perovskite structure,which can be described as consisting of identical perovskite-like blocks,three corner-sharing BO6 octahedra thick,separated by layers of vacant octahedral. These ceramics have high dielectric constants in the range of 48-42,high quality factors (Q×f ) up to 38 000 GHz,and low temperature coefficient of resonant frequencies (-f) in the range of (-40-+6)×10-6 ℃-1. With increasing content of La and Ti,the dielectric constants slightly decrease but -f gradually increases.