Abstract: This paper presents a series of improved algorithm in 8051 to achieve the high reliability computing multi-byte division.The algorithm updates the traditional "shifting-subtracting" algorithm while owns the limitations of the unsigned multi-byte division,and it solves the overflow problem.And via experiments,the accuracy of results proves correct.The algorithm is simple,and with strong adaptability,high reliability and very good practicality.

Key words: SCM； assembler instruction； multi-bytes’ division；