Abstract: ILSP （interlaced inner and outer loop software pipelining） is an efficient algorithm of optimizing nested loops.To ensure the ILSP a good time efficiency and a good space efficiency,there must be an efficient nested loop control mechanism to support the algorithm.The control mechanism designed is realized mainly by hardware.It avoids adding many extra instructions and makes the II （initialization interval） of each loop in the nested loop least.Cooperated with the complier,the mechanism can efficiently support the software pipelining of the nested loop,and can ensure the ILSP a high speedup and a low space cost.