中文摘要：

讨论了共轭梯度法（Conjugate Gradient,CG）在l2模意义下的单调性与收敛性.所得结论对结合共轭梯度法来求解大规模线性方程组的各类方法,特别是对研究外推瀑布式多重网格法（EXCMG）按l2模的收敛性有重要作用.

英文摘要：

The monotonicity and convergence of the conjugate gradient method are discussed（CG） in the sense of l2-norm.The results have an important role in studying of the convergence of all kinds of methods for solving large-scale linear systems combined with CG,especially for the convergence of the extrapolation cascadic multigrid method（EXCMG）,in the sense of l2-norm.