Abstract: The changes of chlorophyll content, fluorescence characteristics and expression of photosynthesis-related genes in two peanut cultivars (Yueyou 7 and Shanyou 523) subjected to simulated drought stress were investigated by the treatment of trichostatin A (TSA), a histone deacetylase inhibitor. The results show that the response of Yueyou 7 to drought stress on total electron transfer rate (ETR) and PSⅡ quantum yield (PSⅡ) is stronger than that of Shanyou 523. High photosynthetic efficiency of both cultivars of peanut can be maintained under drought stress with the treatment of 1mol/L TSA for 12h. Meanwhile, with the treatment above, the expression level of AhLHCB3 and AhPORA increases significantly, while that of AhRuBP decreases. The response trend of both cultivars to drought stress under the effect of TSA is similar but different in response level and time.