Both high and low temperature (40℃ and 4％)have evident effects on peroxidase isozymes in Robinia pseudoacacia seedlings. As compared with what is at the con-trol(25℃), peroxidase activity in Robinia pseudoacacia Seedlings rises to 165.5 and 155% at high and low temperature respectively. In addition, low temperature induces the formation of a slow-migrating peroxidase isozyme (electrophoretic mobility being 0.06), whereas high temperature promotes the synthesis of fast-migrating peroxidase isozymes (electrophoretic mobilities being 0.26, 0.56 and 0.67) and causes the disappearance of two slower-migrating peroxidase isozymes (electrophoretic mobilities 0.10 and 0.17). Synthesis of any protein is an expression of gene, so changes in tempra-ture can induce variation in the expression of individual genes, resulting in syntheses of some enzymes adapted to given temperatures. This may have something to do with the biochemical mechanism of higher adaptability to environmental stress of Robinia pseudoacacia.