Abstract: Conventionally, the lithium conversion rate of nuclear class resins was measured by measuring the lithium concentration after eluting lithium from the ion exchange resin with acid, which is with the problems of long analysis time and lowered analysis results. In this study, the microwave digestion-atomic absorption spectroscopy was applied in the measuring of lithium conversion rate of nuclear class ion exchange resin. The nuclear class ion exchange resin was completely digested by microwave. The lithium conversation was measured by atomic absorption spectroscopy. The lithium conversion rate was calculated, combined with the working exchange capacity of the hydrogen type ion exchange resin. Under the optimized conditions, the recovery of standard addition, relative standard deviations and the lithium conversion rate were 99%, 0.97% (n=7) and 99.20%, respectively. The system has the advantage of less usage of ion exchange resin and accurate analysis result, which demonstrate that the present system can be applied in the measuring of lithium conversion rate of nuclear class ion exchange resin.