The study aimed to evaluate inhibition effect of sclerotia of Polyporus umbellatus Fries aqueous extract (SPUE) and polyporus polysaccharide (PPS) on bladder cancer, then to measure their effect on mRNA expression of glutathione S-transferase π (GSTPi) and NAD(P)H:quinone oxidoreductase 1 (NQO1) in female Fischer-344 rats model. The model rats were induced by N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) for a period of 8 weeks and saccharin for 12 weeks. SPUE (50 mg/kg, 250 mg/kg, 500 mg/kg) and PPS (28 mg/kg) were orally administrated to the model rats during the whole study. Compared to the control group, a more preventive effect of SPUE and PPS treatment on bladder cancer was discovered, higher mRNA upregulation of GSTpi and NQO1 was seen in the treatment group. Furthermore, the GSTPi and NQO1 mRNA upregulated level in the low-dose group (SPUE 50 mg/kg) was at maximum. In brief, SPUE and PPS are highly effective in inhibiting bladder carcinogenesis in rats, which may be associated with upregulation of GSTPi and NQO1 in the bladder.