Several mechanisms were involved in the occurrence of MDR in cancer cells, the major cause was chemotherapy agents translocated from intracellular to extracellular, leading to the concentration of the anticancer agents reduced markedly, the phenomenon might chiefly attribute to P-glycoprotein (P-gp) which cause the agents outflow from the resistant cells actively (Weisburg et al., 1999). The gene discussed is ABCB1; the disease is cancer.