In data warehouses , some of query responses are stored to accelerate the response time of analytical queries . Materialized views are the response of queries stored in data warehouses . Materialized views should be changed according to changes in basic relations . Different view maintenance expressions have been presented for maintaining materialized views. In this paper a new algorithm is presented to produce the improved view maintenance expression . The proposed algorithm consists of two parts . In the first part , the algorithm constructs a tree to reduce the number of accesses to big data sources and in the second part an improved view maintenance expression is presented according to the constructed tree and the amount of changes in data sources . Experimental results show that the improved view maintenance expression reduces the data warehouse maintenance time and the data warehouse maintenance cost in comparison with previous methods .