Yttrium Iron Garnet (YIG) has been used as an important material in the Circulator/Isolator which is used in RF communication system, mobile phone, and satellite broadcasting, etc. In this study, we investigated the variation of electromagnetic properties of YIG ferrites for Isolator/Circulator application with Zr addition. The YIG ferrites, Y2.1Ca0.9Fe4.4-xV0.5In0.05Al0.05ZrxO12 With x=0, 0.05, 0.1 and 0.2, were prepared by the conventional ceramic sintering process. The Zr-substituted YIG ferrite, Y2.1Ca0.9Fe4.4-xV0.5In0.05ZrxO12, showed the highest saturation magnetization (1097 gauss) at x=0.1. Good microwave properties were shown as isolation of 18.60 dB and insertion loss of 0.45 dB at x=0.2. In addition, the ferromagnetic resonance (FMR) linewidth decreased as Zr content increased.