OBJECTIVE:To establish a method of the uncertainty evaluation of the potency testing of Oxytocin injection. METHODS:Mathematical model was established for potency testing of Oxytocin injection to analyze the influential factors of un-certainty. The uncertainty components were quantitatively analyzed and the uncertainty was calculated. RESULTS:The expanded un-certainty of the potency testing of Oxytocin injection was 0.20 u/ml and the potency was(9.29±0.20)u/ml,coverage factor K=2. CONCLUSIONS:The method is suitable for the uncertainty evaluation of potency testing of Oxytocin injection.