This paper describes an object-oriented development method and an optimization method for embedded control systems. In embedded control systems development, specifications are changed frequently and there is strong constraint of memory. We present an object-oriented analysis and design method based on polymorphism patterns. Polymorphism patterns are standard of a method interfaces which are shared by several objects. With this method, a system is constructed with objects which have polymorphism patterns. This system ensures reusability because it easy to replace objects where the specification of the system is changed. Object-oriented technology has several functions, such as instantiation, inheritance and polymorphism, where functions are implemented with both method-tables and inheritance hierarchy tables. But these mechanisms are needless, in the automotive engine control application which execute fixed control flow. Our optimization method eliminates these mechanisms and reduces executable code size. We have applied above techniques to the development of automotive engine control applications.