The aim of this study was to investigate the effects of β-catenin on the tumorigenicity of K562 cells in vivo. The β-catenin expression in K562 cells was down-regulated through sequence-specific siRNA, and the treated K562 cells were implanted into BALB/c nude mouse subcutaneously. And the tumor-forming rate and tumor-forming curve (interference group) were observed. Experiments were divided into 3 group: interference group (implanted K562 cells transfected with β-catenin interfering plasmid DNA), control group (implanted K562 cells transfected with unrelated sequence plasmid DNA) and untreated group (implanted K562 cells transfected without plasmid DNA). The results indicated that the tumor-forming rates of untreated group (n = 9), control group (n = 8) and interference group (n = 9) were 100%, 87.5% and 0% respectively. The tumor-forming rate of interference group was significantly lower than those of the other 2 groups (p < 0.001). Comparison of the tumor-forming curve between 3 groups, showed that in first 2 groups existed tumor-forming and their final tumor volumes were almost the same, but the tumor growth of untreated group was faster than that in control group; while in the interference group there was not tumor-forming. It is concluded that the β-catenin expression level in K562 cells is down-regulated through the interference of sequence-specific siRNA, thus affecting their tumor-forming potential in vivo.