To develop high temperature shape memory alloys, the effects of Iridium, (Ir) on the constituent phases and the phase transformation temperature were investigated for PtTi intermetallic compound. Pt50-xIrxTi50 alloys with Ir contents between 0 and 37.5 at% were prepared by arc melting method. The phase constitution and the phase transformation temperature were investigated by X-ray diffractometry (XRD), microstructure observation by an optical microscope, and differential thermal analysis (DTA). It was found that the B19 phase appeared up to 37.5at%Ir in Pt-Ir-Ti and the phase transformation temperature raised from 1303 K in PtTi to 1473 K in the Pt-37.5Ir-Ti.