The miscibility of perdeuterated isotactic polypropylene (d-PP) and ethylene-1-hexene random copolymer (EHR) blends, which were polymerized by metallocene catalyst, was investigated by small-angle neutron scattering (SANS) with changing hexene content in EHR and temperature above the melting point of d-PP. Flory-Huggins interaction parameter (chi (d-PP/EHR)) between two polymers was determined on the basis of random phase approximation (RPA). It was revealed that chi (d-PP/EHR) decreases with increasing hexene content in EHR, which contain hexene ranging from 26 to 46 mol %, and with increasing temperature; however, the chi parameter between d-PP and atactic poly(l-hexene) was larger than that between d-PP and EHR with 46 mol % of hexane, and it increased with increasing temperature. Scattering intensities from d-PP and isotactic poly(1-hexene) blend could not been explained by RPA, being concluded that these two polymers are immiscible.