In order to update the core attributes of decision table dynamically, when the decision table object is modified, the storage structure of equivalence class list table of decision table was constructed, and the definitions of the simplified decision table and core attributes based on the simplified decision table were proposed. It was proved that the core attributes acquired from the definition is equivalent to core attributes of positive region. And then, the theories of updating core attributes, which aims at the aspects of modified the object appointed, were researched. The corresponding algorithm was described, which on the base of simplified decision table, only needs to search the part of equivalence class list table to obtain the modifying object, reduces the search range and enhances the efficiency of the algorithm. The method of counting core attributes was used to avoid storing discerniblity matrix and reduce the space complexity. Finally, the validity of the algorithm was verified in instances.
