Objective To explore the mechamism of treating leukemia with Yiqi Yangyin formula. Methods We hatched cell lines K562 with human leukemia by means of serological pharmacology. At the same time, Yiqi Yangyin formula is given to the rats. And then, we observe rats' serum's effects on membrane fluidity, cell cycle and bcl-2 gene and mutant p53 gene expression of cell lines K562 by fluorophotometry, flow cytometry and immunohistochemic. Results Serum of the rats given Yiqi Yangyin formula at lower drug concentr...