The present disclosure relates to a method and system for file processing. The file processing method may include the steps of scanning a source files, identifying a target code block, and generating a first abstract syntax tree (AST) reflecting the structure of the target code block. The file processing method may further include the steps of identifying a position to place a plugin code, placing the plugin code into the first AST, generating a second AST reflecting the structure of the target code block with the plugin code, and using the write-back interface to write the second AST into the source file. The present disclosure may improve the efficiency and enhance the flexibility of the file processing system.