Microwave dielectric properties of A-site substitution by both La 3 + and Nd 3 + in (Pb 0 . 5 Ca 0 . 5 )(Fe 0 . 5 Nb 0 . 5 )O 3 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution of [(Pb 0 . 5 Ca 0 . 5 ) 1 - x (La 0 . 5 Nd 0 . 5 ) x ](Fe 0 . 5 Nb 0 . 5 )O 3 + δ (PCLNFN) were improved because the solid solution of small amount of surplus (La, Nd) 3 + with (Pb, Ca) 2 + could eliminate oxygen vacancies; the formation of secondary phase (pyrochlore phase) was also caused by surplus (La, Nd) 3 + . The decreasing of dielectric constant with the increase of (La, Nd) 3 + content was due to the formation of pyrochlore phase. Qf values were almost unchanged at x=0.02-0.08, but the temperature coefficient of resonant frequency (TCF) was decreased. Typically, at x=0.06, the excellent microwave dielectric properties of Qf=5822 GHz, r =99.9 with TCF=0 ppm/ o C were obtained.