Abstract:High performance liquid chromatography (HPLC) was adopted to analyze the content of endogenous hormones such as zeatin(ZT), gibberellin(GAs), auxin(IAA) and abscisic acid(ABA) in male fertile plants and male sterile plants of maize derived from sister-cross population, which was produced with male sterile mutant induced by space flight. Exogenous GAs treatment was applied to plants of sister-cross population of maize,and the fertility of the maize plant both in the exogenous GAs treatment plots and the control plot was investigated. The results showed that the fertility segregation ratios of sister-cross populations did not change with exogenous GAs treatment. At the seedling stage, only the differences of IAA and ABA contents in leaf between fertile and sterile plants were significant at the 0.05 level, and the differences of ZT, GAs, IAA and ABA contents between sterile and fertile plants all were at 0.05 or 0.01 level significant,at the jointing stage. At the uninucleate microspore stage the differences of IAA and ABA contents in anther were significant at 0.01 level, but at the binucleate pollen stage only the difference of ABA content was significant at 0.01 level. During the four different developmental stages, the contents of ZT, GAs and IAA were higher in fertile plants than in sterile plants, but the content of ABA was lower in fertile plants than in sterile plants in the two different tissues. It was concluded that exogenous GAs treatment could not alter the fertility of maize plants, so this mutant did not belong to the GAs sensitive type. The changes of the hormone level or the hormones ratio might be related to the pollen abortion of the male sterile material used in this experiment, and it seems that ABA and IAA may have a closer relationship with the fertility expression of the material used in this experiment than ZT and GAs according to the significance tests.