Abstract: This article had studied the biomass, seasonal dynamics, the vertical distribution, decomposition and turnover of the fine roots in Larix olgensis plantation of Changbai mountain from May 2006 to 2007 by using the sequential soil coring method and litter bag technique. The results showed that the average biomass of fine roots was 3.825 7 t/hm² with 84.51% living fine roots and 15.49% dead fine roots. The fine roots mainly distributed in the 0-10 cm of soil layer with 72.09% living fine roots and 50.46% dead fine roots. And with soil layer deepen,the fine roots biomass decreased. The annual change of living and dead fine roots biomass in Larix olgensis plantation had obviously seasonal variation. The living fine roots biomass in different season varied with a double peak curve, and the peaks of the curve appear in May and August. The seasonal change of the dead fine roots biomass showed a multiple peak curve. The average decomposition efficiency(k)was 0.001 5 for Larix olgensis plantation. Net primary productivity, decomposition and annual turnover of fine roots in Larix olgensis plantation were 1.534 8 t/hm², 0.145 0 t/hm² and 0.47 times per year, respectively.