The features of volcanic movement and volcanic clastic rocks has been illustrated, and by measuring the carbonized wood and by the periodical division of volcanic eruption since Holocene Quaternary, some scientific basis for studying volcanic calamities in Changbai Mt. has been provided in this paper. By the measure of carbonized wood found in volcanic scarp, it can be divided into six periods of eruptions, that is, Bingchang period (7 800 Y. ago), Yuanchi period (6440 Y. ago), Erdaobainhe period (3 450 Y. ago). Xiaoshahe period (1 400 Y. ago), Naitoushan period (1 000 Y. ago) and Tianchi period.90-300 Y. ago). Up to now it can be said that the examination of carbonized wood is a good method for researching forest fire caused by volcanic eruption. With this method it can be seen that there were three times of big eruptions in Changbai Mt. since Holocene Quaternary, which were in Yuanchi period, Xiaoshahe period and Naitoushan period. The biggest one happened in Naitoushan period, with fired area of 70km² and disforested woods of 2.1 miillion m³. From the recent data of Tianchi volcano, it is indicated that the movement of earth crust is still active and strong. So it should be considered that the Changbai Mt. is not a "dead volcano", but a potential "active volcano".