La0.7Ca0.2Sr0.1MnO3/xIrO2 (LCSMO/xIrO2) compounds were fabricated by solid state reaction method. X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Dc four probed method were used to investigate the structure, magnetic and magnetotransport properties. The results show that at low doping level (x≤0.15) IrO2 goes into the perovskite lattice substituting Mn in LCSMO, but at high doping level (x≥0.20) some part of the IrO2 substituted for Mn4+ in LCSMO lattice and the remainder resided in the grain boundaries in the form of IrO2. LCSMO/xIrO2 composites are influenced remarkabled by the IrO2 doping. With increasing IrO2 addition, the magnetic moment (s) decreases and Curie temperature (TC) decreases first, and then rises slowly of the compounds; In the doping range of 0~0.35, the resistivity rises first, and then decreases slowly, furthermore, the resistivity versus appears double peaks with increasing IrO2 addition. At room temperature, the magnetoresistance (MR) of the composites have been improved remarkably.