The results and new technology proposal of applying object-oriented technologies to embedded control software are discussed in this paper. There exists following obstacles when we apply object-oriented technologies to embedded control software: (1) the analysis and design method for control algorithms find the method of reusing them as software components, and (2) the size reduction method reserving advantages of object-oriented technologies. We propose solutions for each of them. First, we extend the usual object-oriented analysis method. The object structures are identified based on the structure of the control algorithms. Second, we give hierarchical implementation architecture on the small microcomputers. We use assembly language at the lower level of this architecture, and the use of C++ language is restricted only at the upper level. We show this mixed use of object-oriented language with assembly language gives the expected balance of productivity and performance.