There are several input method frameworks along with corresponding implementations coexisting on Linux. The situation indicates inadequateness of existing standardizing effort focusing on input method protocol. However, IME (input method engine) interface standard developed by China Linux Standards Group introduces a brand new way to standardize input method, and makes it possible to develop an adaptive IME working on different frameworks. Based on the survey and synthesis of the existing input method frameworks on Linux, rationale and benefit of IME interface standardization are analyzed. Features and design principles of the standard are expounded. Entities related to input method are partitioned into four portions. Runtime mechanisms of each portion as well as interactions between different portions are analyzed in detail by means of event flow chart. Feasibility of the standard is demonstrated by sample IME implementations. Three sample implementations that cover different aspects of IME interface standard are briefly summarized. The design and developing practice can be referenced in developing compliant IME. Finally, the prospect of promising applications and future working directions are proposed.