Polypropylene (PP) is one of the most used polymers for microporous membrane fabrication due to its good thermal stability, chemical resistance, mechanical strength, and low cost. However, the hydrophobic nature of PP membrane greatly limits its application, e.g., being susceptible to fouling when applied in an aqueous application, and suffering from wetting when used as battery separator or membrane contactor. To address these issues, numerous efforts have been devoted to the hydrophilic modification of PP membrane. In this work, PP was blended with different amounts of submicron sized hydrophilic titanium dioxide (TiO2) particles and then cast into oriented composite films under elongational flow. The as-cast composite films were fabricated into the microporous membranes according to the common dry stretching strategy same as that of the pristine PP film. Scanning electron microscopy (SEM) results showed that the composite membranes possessed two types of pores, one being due to the lamellar separation and the other ascribed to the debonding of the fillers from the PP matrix. Water vapor transmission rate (WVTR) measurements showed the permeability of the composite membranes was improved when the TiO2 content was more than 20 wt% due to the presence of slightly larger detaching pores as well as the surface polarity of TiO2 particles, which facilitated the adhesion of the water vapor molecules. Consistently, reduced water contact angle can be observed for the PP/TiO2 composite membranes, compared to that of the neat PP membrane.