Scientific computing application codes have integrated the results of scientific computing research. Because of the requirements of specific scientific fields for large scale and highly efficient computing, the development of application codes is very different from that of the usual computer application software. Currently, the development of application codes is becoming more and more dependent on combining both the application and high performance computing. New ideas should be studied and new methods proposed to simplify and speed up the development process. This paper outlines the main characteristics of application codes, analyzes the key problems that need to be solved, and discusses new ideas and methods for their development.