With the development of VLSI technology, a single chip can contain over one billion transistor. Multithreading technique is the developing trend of high performance processor in the future. A novel processor architecture and implementation scheme of the simultaneous multi-microthreading(SMMT) that combines simultaneous multithreading technique with microthreading technique is proposed in this paper. SMMT efficiently combines the advantage of little hardware overhead in simultaneous multithreading with the ability of speeding up single program in micro-threading. SMMT can exploit the microthreading-level parallelism of single program fully by means of software and hardware co-design. Simultaneous multi-microthreading architecture is implemented on Godson-2 processor to evaluate performance. The evaluation results show that simultaneous multi-microthreading speeds up the execution of a single program significantly. It improves the performance of microprocessors with little hardware overhead.