The increasing amount of data in the database makes it time-consuming and laborious for users to query using the database system. The traditional query optimization method has been unable to meet the requirements of today's data query, thus improving the efficiency of database system optimization has become a hot spot of research. In this paper, the distributed query processing tech- nology based on the semi join algorithm is proposed to optimize the database system. This paper selects the semi join algorithm to optimize the algorithm design, proposes the semi join operation query optimization algorithm (SDD-1), and verifies it by experiment to calculate the cost of the query algorithm. The results show that the query optimization strategy can significantly reduce the trans- mission cost and improve the overall efficiency of query.