Abstract: Annual lamination plays an important role in the research of environmental changes. Through coring a sample mud column without disturbing it in the lacuster of Angulinuo Lake, getting some thin sections from the core, and observing the sections under scanning electronic microscope, the researchers have discovered annual laminations of grain size that are made up of lacustrine deposits and eolian deposits, and the eolian deposits are transported by winter monsoon. By counting the layers the researchers have set up a time scale of annual laminations, and by calculating the grains in each layer the researchers have reconstructed the palaeoenvironment around Angulinuo Lake since 8507 a B.P. During 8507-5429 a B.P., the winter monsoon was weaker; but in the latter time of the period, the monsoon was unstable. During 5429-3244 a B.P., the winter monsoon was stronger. In 3244-2494 a B.P., the winter monsoon became weaker. In 2494-1165 a B.P., winter monsoon became a little stronger. Since 1165 a B.P., the winter monsoon has become weaker. The changes of winter monsoon reflected by annual laminations of grain size in Angulinuo Lake correspond well to the environmental changes in the northern area of China and to the changes of the sea level in the same period.The weak period of the winter monsoon responds to the period of high sea level; while the strong period of the winter monsoon corresponds to the new periglacier stage and the period of the low sea level. And the unstability of the winter monsoon is in accord with the unstability of environment in existance in in the northern area of China.