Abstract: To investigate the effect of ethephon on internode elongation and endogenous hormones in different genotypes of maize, 12 commonly used inbreeding lines of maize were sprayed with 200 mg/L ethephon at jointing stage.The results showed that,after the treatment of ethephon,five inbreeding lines (Zheng 58,L6M,K12,Yu-zi 87-1 and 8085 Tai) had no significant differences for the characters compared with the control,the other inbreeding lines showed significant difference in plant height,ear height and length of the third to fifth internodes,decreased contents of endogenous hormone IAA and ratio of GA4/ABA,and increased contents of endogenesis hormone ABA,comparing with that of the control;while the contents of endogenesis hormone GA4 showed no significant variation.Among different inbreeding lines,morphology indexes as the plant height,ear height and internodes length,content of IAA and ABA,and the ratio of GA4/ABA showed remarkable differences,ranging from 6.41% to 102.64%.Each index could reflect the sensitivity of different maize genotypes to ethephon treatment.Among the 12 inbreeding lines,Chang 7-2,Xun 928,Mo17 and Dan 340 showed higher sensitivity to ethephon,while Zheng 58,L6M,K12,Yu-zi 87-1 and 8085 Tai showed lower sensitivity to eyhephon.