Seeds germination or dormancy is strictly controlled by endogenous phytohormone signal and environment cues. High temperature (HT) suppresses seeds germination or triggers seeds dormancy but underlying mechanism by which HT mediates seeds germination thermoinhibition needs more investigating. SOM is reported as the critical factor negatively controls light-irradiation seeds germination by altering Abscisic acid (ABA) and gibberellin acid (GA) biosynthesis. Here we found that HT accelerates SOM expressing through ABA signal transduction component ABI3， both of abi3 and som mutants seeds show high germination rate under HT in contrast to wild type seeds. Using ABI3 as the bait， we identified the epigenetic factor Powerdress (PWR) as the ABI3 interaction protein. Genetic and physiological analysis showed that PWR negatively control the expressing of SOM， and overexpressing PWR enhanced， while pwr mutant reduced， seeds germination thermotolerance. Without HT stress， PWR accelerated the histone H3 deacetylation level and H2A.Z deposition at SOM locus， and thus suppressed ABI3-dependent SOM transcription for seeds germination， HT stress block PWR transcriptional level， thus attenuated the inhibition effect of PWR on SOM expressing， resulting into seeds germination thermoinhibition. Thus our finding propose a new function of PWR in controlling seeds germination under HT through histone acetylation modification and H2A.Z deposition.