When the .NET Framework platform developed software systems,it generally used a particular algorithm to achieve the encryption of sensitive information.This affects the scalability and maintainability of software.To this end,studied the inheritance hierarchy for the .NET Framework symmetric algorithm class,analysed its process of the encryption and decryption, proposed a assumption of general symmetric algorithm encryption class,and made a feasibility analysis.Then introduced the composition of the general symmetric algorithm encryption class, explained the design ideas of the various members,and gave the complete code achieved through VB.NET.Finally used an example to show that this class is very convenient and its designing ideas can be extended to other encryption algorithms.