Abstract: In order to explore the fast-growing mechanism of Pinus strobus,one year old,three-year-old and fiveyear-old of Pinus strobes,Pinus koraiensis and Larix olgensis were selected as experimental materials,the contents of indoleacetic acid（IAA）,zeatin（ZT）,gibberellin（GA）,abscisic acid（ABA）and salicylic acid（SA）in new shoots of Pinus strobus,Pinus koraiensis and Larix olgensis were measured in June,July and August.The results showed that the contents of IAA,ZT and GA in three tree species were all lower than 0.001μg·g-1,and the order of ABA content in the three tree species was Pinus koraiensis＞Pinus strobus＞Larix olgensi,the annual cycle of Pinus koraiensis was decreasing in June,the lowest in July and increasing in August;the content of ABA in Pinus strobus and Larix olgensis was the highest in June,and decreased to the lowest in August;the content of SA in the three tree species was in the order of Pinus strobus ＞Larix olgensis＞Pinus koraiensis,and increased with seedling age in the same tree species,and the content of SA increased from June to August.