Abstract: The effects of water stress on the chlorophyll fluorescence parameters in the leaves of “Tieguanyin” and “Fudingdabaicha” tea cultivars were investigated. The results show that under water stress, the minimal fluorescence (Fo) of tea plants increases significantly, while the maximal fluorescence (Fm), variable fluorescence (Fv), light energy transformation efficiency of PSⅡ (Fv/Fm) and activity potential of PSⅡ (Fv/Fo) decrease markedly, suggesting that PSⅡ reaction center is destroyed by water stress. Photochemical reaction rate (P_rate), fluorescence increment time (T_1/2) and electron transport rate (ETR) decrease, leading to increased thermal dissipation rate (D_rate), non-photochemical quenching (qN) and relative limitation of photosynthesis (L_PFD), but obviously decreased photochemical quenching (qP) and actual photochemical efficiency of PSⅡ (Yield). The tea cultivar “Tieguanyin” has stronger stress tolerance and higher PSⅡ photochemical efficiency than “Fudingdabaicha” .