Highly purified hydrogenous ring poly(4-trimethylsilylstyrene) (h-PT) and deuterated ring polyisoprene (d-PI) samples as well as their linear counterparts were prepared, and the miscibility of three kinds of polymer blends, i.e., linear linear, ring linear, and ring ring, denoted as L-L, R-L, and R-R, respectively, with all 50/50 vol % was evaluated by small angle neutron scattering (SANS) measurements. PT and PI are known as a miscible polymer pair with lower critical solution temperature (LCST) type phase diagram. At low-g regime of the scattering profiles, R-R blend exhibits much higher scattering intensity than L-L and R-L, while the latter two show similar profiles. Moreover, from Zimm's analysis, the spinodal temperature of R-R was estimated to be about 100 degrees C lower than the other two blends, L-L and R-L. These results suggest that the miscibility of R-R is considerably lower than the other two blends, which is a clear manifestation of the topological effect on the phase behavior of the present blend.