Abstract: A systematic study was conducted to explore the causes of seed dormancy of 4 species in Acer genus and the corresponding methods for dormancy breaking. The results showed that the fruit pericarp of the 4 species had good water permeability, which suggested that pericarp permeability was not the main reason to inhibit seed germination. The vitality test of the invitro embryo showed that the embryo of Acer seeds didn′t undergo dormancy. Among the dormancy breaking treatments, the low temperature stratification taken directly with the dry seeds requested the longest time, the time needed for dormancy breaking was obviously shortened by soaking the seeds in gibberellic acid (GA) solution or in pure water for 36h before the low temperature stratification. But there was no significant difference between the methods to soak the seeds in GA solution or in the pure water for 36h. The tests also showed that the seed soaking time duration in GA solution did not impact much on dormancy breaking effect. The seed dormancy for Acer rubrum and A. palmatum could be overcome by soaking the seeds in GA solution for 48h and followed by 10 days stratification with alternating temperature, and the time required was much shorter than that of needed with regular low temperature stratification. Therefore, it was concluded that the better treatment to break the seed dormancy for the above two species would be soaking the seeds in GA solution combined with alternating temperature stratification.