AIM: To study the effect of Haimiding on the functioning of red cell membrane of FC and H22 tumor-bearing mice.METHODS: The membrane fluidity of red cells is measured with DPH fluorescence probe as a marker; the amount of red cell membrane proteins is measured using polyacrylamide gel electrophoresis; the amount of sialic acid (SA) on the surface of red cell membrane and the sealability of these cells are measured using colorimetric analysis.RESULTS: Haimiding can lower the membrane fluidity of red cells in tumor-bearing mice and the amount of their membrane proteins, while increasing the amount of sialic acid in the membrane of red cells in these mice and enhancing the ability of the membrane of their red cells to reseal.CONCLUSION: The anti-tumor effect of Haimiding on tumorbearing mice is due to its ability to improve and restore the functions of the membrane of their red cell and to enhance the immune effect of the organisms.