Abstract: Experiments were conducted under artificial climate chambers conditions to assess the photosynthetic responses and photosynthetic capacity recovery process of early rice （Oryza sativa L.，Jinyou458） to low temperature stress （T1 and T2， subjected to 17°C and 15°C for 3 days） at spikelet differentiation stage， by determined gas exchange and light response parameters， SPAD value， yield components. The results indicated that， （1）Pn， Gs， Ci， Tr of T1 and T2 were decreased significantly compared with CK （control group， natural condition）. Pn of T1 recovered 3 days after stress， while T2 recovered 6 days later. However， Pn and Gs was decreased significantly on the 17th day and 32nd day after stress， while Tr was increased significantly. （2）Light response capacity of T1 enhanced 0-6 days after stress， while T2 was decreased significantly. By the 6th day， T2 was recovered to the same level of CK， but Pm， AQY and Ik of T1 and T2 were decreased significantly by the 32nd day. （3）SPAD value of T1 and T2 were decreased significantly. T1 was recovered to the same level of CK by the 3rd day， while T2 recovered by the 6th days. （4）The grain No. per panicle， ripening rate， thousand grain weight， and theoretical yield of T1 and T2 were decreased significantly， while unfilled and abortive grain rate were increased， which leaded to yield reduction rate of 25%. Obviously， low temperature stress at spikelet differentiation stage had negative effects on gas exchange activity and maximum photochemical capacity of early rice， thought recovered to some degree later， but the negative effects were irreversible for long， which leaded to lower yield. The results could support scientific foundations for meteorological disaster impact assessment and meteorological disaster indexes development.

Key words:  Spikelet differentiation stage, Low temperature stress, Photosynthesis, Yield components