Phellinus linteus (Hymenocaetaceae) is a member of Basidiomycotinae, which has been used for the treatment of gastric cancer, non-insulin-dependent diabetes mellitus, diarrhea, and menstrual irregularity. To investigate the diuretic action of Phellinus linteus, urinary volume, serum parameters and urinary electrolytes in HgCl$_2$-induced acute renal failure rats in vivo were measured. The results showed that its MeOH extract produced significant increases on urinary volume, sodium and potassium excretion, and revealed lowering effects of the abnormally elevated BUN, creatinine and uric acid value in acute renal failure rats.