This study was aimed to investigate whether the inhibition of NHE1 activity and intracellular acidification can reverse resistance of leukemia cells to the imatinib and to explore downstream signal molecule networks of BCR/ABL in the cells of chronic myelocytic leukemia (CML) patients. The mRNA and protein expression of P-glycoprotein (Pgp) and the drug accumulation were assayed after acidifying the primary leukemia cells of patients or K562/DOX and K562/G01 cells. The effects of intracellular acidification of primary leukemia cells on the phosphorylation level changes of ERK1/2 and p38 MAPK were analyzed by Western blot. The results showed that the intracellular concentration of drugs in the advanced patients increased and the sensitivity of K562/DOX and K562/G01 cells to imatinib was enhanced after intracellular acidification or treatment with NHE1 inhibitor cariporide. With downregulation of intracellular pH, the phosphorylation of p38 MAPK decreased in advanced patients and the phosphorylation of ERK1/2 increased within 3 min and then decreased after 30 min. SB203580, the specific inhibitor of p38 MAPK, displayed a synergistic effect with the inhibitor of NHE1 to downregulate the mRNA and protein expression of Pgp. It is concluded that the inhibiton of NHE1 can significantly decrease the protein expression of Pgp in K562/DOX and K562/G01 cells, increase the accumulation of Rhodamine123 and doxorubicin in the cells of advanced patients and enhance the sensitivity of cells to imatinib in which the p38 MAPK signal transduction pathways involves.