Sodium formononetin-3′-sulphonate (Sul-F) is a water-soluble derivate of formononetin, and an increasing number of studies have shown that Sul-F not only possesses favorable water solubility but also exhibits good lipid-lowering and bioactivities. In the current study, the toxicity of Sul-F was evaluated in dogs after 90-day intravenous infusion. Dogs were treated with Sul-F at dose of 0, 33.3, 100, and 300 mg/kg, and observed for 90-day followed by 28-day recovery period. Weekly measurement of body weight, temperature and food consumption were conducted. Ophthalmoscopy, ECG examination, urinalysis, serum biochemistry and hematology examination were performed at pre-test, on days 45 and 90, and following by 28-day recovery period. Histological examination was performed on day 90 and 28-day recovery period. No mortality, ophthalmic abnormalities or treatment-related findings in body weight, clinical chemistry, hematology, and histopathological examination were detected. However, a white crystal (non-metabolic Sul-F), transient vomiting and recoverable vascular stimulation were observed in 300 mg/kg/day Sul-F treated dogs. Under the conditions, the no-observed-adverse-effect-level (NOAEL) for Sul-F was 100 mg/kg in dogs.