This study aimed to evaluate the uncertainty of simultaneous determination of lead (Pb), cadmium (Cd) and arsenic (As) in cosmetics by microwave digestion-inductively coupled plasma mass spectrometry (ICP-MS) with 72Ge, 115In and 209Bi as intal standards. According to the method of Safety and Technical Standards for Cosmetics (2015), a mathematical model was established to evaluate the sources and components of uncertainty for the determination of lead, cadmium and arsenic in cosmetics. The results showed that the uncertainties in the determination of lead, cadmium, and arsenic elements in cosmetics were (10.1±0.6) mg/kg, k=2, (4.84±0.28) mg/kg, k=2, (2.04±0.18) mg/kg, k=2, respectively. The main factors that affect the uncertainty of determination results were standard substance, calibration curve, recovery and measurement repeatability.