The crystal structure and dielectric properties of Pb 1−x Ca x (Yb 0.5 Nb 0.5 ) 1−x (Fe 0.5 Nb 0.5 ) x O 3 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) have been investigated in this paper by X-ray diffraction (XRD), dielectric and Raman spectroscopic measurements. The crystal structure of Pb 1−x Ca x (Yb 0.5 Nb 0.5 ) 1−x (Fe 0.5 Nb 0.5 ) x O 3 changes from the orthorhombic to the pseudocubic phase with local non-uniform distribution of B-site cations at room temperature when x=0.2. With the further increase of x value, the sample exhibits the phase mixture of pseudocubic phase and Ca(Fe 1/2 Nb 1/2 )O 3 (CFN). The dielectric constant increases with the increase of x value up to x=0.2 and decreases with the further increase of x value. The sample exhibits typical dielectric relaxor behavior when x=0.2 and 0.4.