This study reports the creation of the solid solutions (1-x-y)KNbO3 – yNaNbO3 – xCa2Nb2O7 system, with y=0.50, 0.0≤x≤0.1, Δx=0.025 using solid-state reaction and sintering by conventional ceramic technology. The mechanisms and patterns of formation of the microstructure and dielectric properties of received solid solutions are established. The most probable mechanism of the formation of defects in the structure of (1-x-y)KNbO3 – yNaNbO3 – xCa2Nb2O7 solid solutions was determined.