Leakage rate is a critical metric for evaluating protective efficacy of masks. This paper reviews the current status of experimental methods and numerical simulation studies for assessing the leakage rates of masks, and reveals that leakage rates are related to multiple factors. The inward and outward leakage rates of masks are further compared and analyzed, and the importance of developing a standardized test method for outward leakage rate is emphasized. Finally, future development direction of mask leakage rate assessment is proposed, aiming to realize the scientific and comprehensive assessment on mask leakage rate and provide guidance for formulating public health policies.