Abstract: The fleshy and bolting roots of‘Qishan Touxinhong’（an early-bolting variety）and the fleshy root of‘Xinxiu Sanhong’（a late-bolting variety）were used as materials to discuss the relationship between the change of endogenous hormone content and early bolting of carrot（Daucus carota L.var. sativa DC.）. The results showed that the contents of endogenous hormones in fleshy root decreased gradually on seedling stage. The contents of GA3，GA4，IAA and IPA increased firstly to higher levels and then declined by degrees，while the contents of ZR and DHZR continually declined to the lowest levels and then increased during leaf fast-developing period. The contents of ZR and IAA increased to the higher levels and the other endogenous hormones content declined slowly during root fast-thickening stage. During the long-days in summer，compared with‘Xinxiu Sanhong’，the contents of GA3 or ZR in fleshyroots of‘Qishan Touxinhong’（FRQ）were significantly lower，while GA4 and IAA in FRQ were significantly higher；In bolting roots of‘Qishan Touxinhong’，the contents of IAA and IPA were significantly higher and GA3，ABA were significantly lower than those of in FRQ. As to early bolting，lower content of GA3 and higher content of IAA played positive roles. Furthermore，higher ratios of IAA to ZR，GA4 to ZR led to early bolting of carrot.

Key words: carrot, Daucus carota L. var. sativa DC., fleshy root, endogenous hormone content, early bolting