Abstract: Gibberellin had prominent promoting effects on breaking dormancy of seeds of Fraxinus mandshurica stratified under the condition of warmcold temperature, i.e. warm temperature followed by cold temperature, and cold temperature. One of the reasons was that gibberellin could accelerate rate of development of the embryos of the seeds, especially those which were stratified under the cold condition. Through treating the seeds with GA in the concentration of 100mg per litre or more, It was found that the rate of development of embryos of the seeds stratified at cold temperature could exceed that of seeds stratified at warm temperature. Therefore, GA treatment could substitution for warm temperature conditions of the stratification. GA had no effect on the promoting germination of the seeds stratified under the regime of warm temperature. This indicated that GA treatments could not completely substitute for the cold temperature required by seeds. In addition, the experiment showed that it was more effective to treat seeds with GA than fruits, and the quantity of GA used was much reduced. The gibberellin could be used to treat seeds stratified under the warm-cold and the cold temperature conditions for shortening the dormancy period and promoting the germination of seeds of Fraxinus mandshurica.