We suggested a lightweight AUTOSAR software platform consisting of an AUTOSAR OS and software development tool. This is a new software platform model of the automotive sector. This software development tool is composed of the editing, project management, System Generator tool by extending OSEK OIL 2.5 syntax structure. AUTOSAR OS is extended OSEK/VDX OS by adding system protection functions, real-time scheduling functions, timer processing functions and the additional object classes and attributes. This lightweight AUTOSAR software platform is well suited for developing time-critical application software and can be utilized the application software for controlling automotive parts and modules.