Our recent research is to evaluate how introduction and/or enlargement of microcracks in tumor would effectively decrease the flow resistance in porous tumors. Theoretical simulation results illustrate more than 10% of the flow resistance reduction after introduction of a microcrack and sequential enlargement of the microcrack would result in more resistance reduction. This research is significant to drug delivery in tumors. In convection-enhanced delivery, reduction of flow resistance would minimize backflow of drug-carrying nanofluid along the infusion catheter. While in systemic drug delivery via i.v., a reduction of the flow resistance would effectively lower the interstitial fluid pressure at the tumor central region, therefore, facilitating more drug delivered to the tumor core.