Abstract: Modern forestry aiming mainly at ecological construction needs some new indicators different from the traditional forestry.Based onthe comprehensiveness of forest coverage rate, total standing forest stock, average forest volume, a new indicator called ‘Forest Thickness'(FT) is put forward in this paper.It is the thickness which is reached by using total stocking wood fromforest and trees to cover the total land in one area with its unit being mm.Thisindicatorsolves the problem that the forest coverage rate can not express the level of forest ecological construction comprehensively with its advantage being used easier and clearer in comparing the levels of forestry development among different areas and different periods.As the indicator mark is over 9mm, it means excellentecosystem; 6～9mm does better; 3～6mm does middle; below 3mm is lower.The indicator values of forest thickness are calculated of the world, 17 countries, historic periods and districts of China, and their status qua of forests are compared and evaluated.

Key words: modern forestry, forest thickness, forest coverage rate, development indicator