Abstract: Attribute weight is usually ascertained by decision maker’s experience knowledge According to calculation method of attribute importance degree in rough sets,the paper put forward the method of ascertaining attribute weight which combined weight given by decision maker with attribute importance degree ascertained by rough sets,that is the method of ascertaining attribute weight based on rough sets The method realized unity between subjective experience knowledge and objective situation,thus it can acquire much more ideal result.

Key words: rough sets, weight, attribute independence degree