Abstract: In this experiment heat shock to the CMS line Zhenshan 97A and its maintainer line were performed in seedlings with 2 or 3 leaves or plants at booting stage (8 days before earing). The changes of isoenzyme patterns, pollen constitutions and self-fertility have been detected. The results obtained by electrophoretic analysis showed that heat shock treatment could induce different expression of peroxidase and esterase isozyme in anther tissue, consequently, lead to reducing the distinction of the constitutions of these two isoenzymes between CMS line and its maintainer. On the other hand, observations indicated that heat shock treatment had little effect on the expression of the CMS phenotype if the head differentiation stage of Zhenshan 97A was under normal atmospheric condition. Heat shock treatment to seedlings with 3 leaves and afterwards developing stage, however, might enhance the stability of the CMS character when the head differentiation stage of the CMS line encountered high temperature(daily mean temperature was higher than 30℃). The relationship between the response to heat shock and the pollen fertility transformation induced by high temperature of the CMS line was briefly discussed.