In this paper, Ca5Co4V64+xO24 (x= -0.1-0.1) microwave dielectric ceramics were prepared by the solid-state reaction method. The effects of vanadium ions non-stoichiometry on phase constitutes, sintering behaviors, and microwave dielectric properties were investigated. Phase purity and lattice parameter were analyzed by XRD. Microstructures were studied via SEM and Raman spectroscopy. It was found that the slight V ionic deficiency improved the relative density, the cation ordering degree, and dielectric properties, while the slight V ionic excess deteriorated these parameters. The good microwave properties of epsilon(r) =10.6, Q x f = 72,990 GHz, and tau(f) = 72.4 ppm/degrees C as well as the dense microstructure with uniform grains and clear grain boundaries were achieved for the Ca5Co4V5.95O24 ceramic. Furthermore, the Ca5Co4V5.95O24 - 0.1 TiO2 ceramic possessed the good dielectric properties: epsilon(r) =13.7, Q x f =19,159 GHz, and tau(f)= 0 ppm/degrees C, which could be employed for microwave applications. (C) 2017 Elsevier B.V. All rights reserved.