Abstract: JK drop test and SMC test as a test method for determination of ore crushing characteristics has more and more applications in model selection and process optimization.Material characteristic parameters of A and b obtained from JK drop test or SMC test is a kind of model parameters based on a specific grinding mathematical model.These two parameters itself has no definite physical meaning，although its product A×b can be used as a measure for ability to resist impact crushing of ore，the A×b value of the size of the process meaning can be reflected only by model calculation.To make up for the deficiency，JKTech Company and SMCT Company recently launched a new index of the ore on grindability by SAG：SCSE values.Based on the review on JK drop test，SMC test and using JKSimMet software to simulate SAG process method and principle，a brief introduction of definition，significance and the limitations on the new index was presented.

Key words: AG/SAG, Ore grindability, JK drop weight test, SMC test, Process simulation