Abstract: Aim To discuss the optimization of large database applications systems Methods Brings up the requrements of optimization,analyzes the purpose,guideline,strategy and layers of optimization Gives some technology in optimization together with their effects on characteristics and criteria of databases ystems Results Gives some specific methods of implementation using Delphi3 to develop Client/Server applications Conclusion Methods of optimization can be very complex and numerous,it requires the user not only to understand the technology,but also to be familiar with the application fields,DBMS and the network environment Evaluation of an optimization must be based upon the effect of actual applications