The object-oriented methods are being rapidly accepted as the solution for the software crisis. Object-oriented systems are composed of the integration of independent object modules; their merits are such that it is possible to reuse objects already developed, and that, when changes are required, modifications are restricted to some independent objects such that their affects to other objects are so little. In this paper, we deal with the macro assembler for next-generation microprocessors which has the merits of object methods. Whenever a microprocessor is newly developed, new assembler should be developed or the existing assembler be modified. In the former, it leads to the loss of time and money by the repeated developments, and, in the latter, it causes the problem of inefficient productivity since other modules are to be analyzed for the affections followed by modifications of one module, especially in the existing assemblers. To resolve these problems, the object-oriented macro assembler suggested in this paper consists of independent objects separable such that it shows reusability and reduces the inefficient productivity by minimizing the affects to other objects. Moreover, the object-oriented macro assembler integrates a macro pre-processor into an assembler, and uses automata for analyzing input streams to reduce the compile time.