Isotactic polypropylene(iPP) hollow fiber microporous membranes were prepared via thermally induced phase separation（TIPS）method.The mixture of di-n-butyl phthalate（DBP）and dioctyl phthalate（DOP）was used as diluent.The effects of α（DBP mass fraction in mixed diluent）and β（iPP mass fraction in polymer solution）on pore size distribution of the membrane were investigated by N2-liquid displacement measurement.The connectivity of the membrane was evaluated with membrane tortuosity.It is noted that resulting membrane is apt to possess a narrow pore size distribution.For same β，the mean pore size and connectivity of resulting membrane decrease with increasing α.For α=0.20，with increasing β，mean pore size of resulting membrane increases with subsequent decreasing，while resulting membrane connectivity increases slightly.For α=0.35 or α=0.50，the mean pore size and connectivity of resulting membrane decrease with increasing β.It is indicated that the change of connectivity is attributed to the difference of the membrane topology.It is shown that membrane pore size and connectivity can be controlled effectively by choosing proper α and β.