The decimation attack is also studied if the minimal polynomial of original sequence is a reducible polynomial. The selecting method and condition of the decimation distance d which can reduce the linear complexity is given. 研究了被采序列的极小多项式是可约多项式的采样攻击问题,给出了能使其采出序列的线性复杂性减少的采样距的选择方法和选取条件。