Abstract: In order to research the effect of ABA and PP333 on frost resistance of Cymbidium seedlings, the Cymbidium goeringii ‘Songmei’ was respectively treated with 20 mg/L ABA and 300 mg/L PP333 ,and then transferred to low temperature(5±0.5℃/0±0.5℃)for 9 days and transferred to nomal condition(22±0.5℃/15±0.5℃) for 12 days.The results showed that: With the low temperature stress,the chlorophyll concentration, the net photosynthetic rate (Pn), the stomatal conductance(Gs),the stomatal limitation(Ls),the PSⅡmaximal photochemical efficiency(Fv/Fm),the photochemical quenching coefficient(qP), the quantum yield of PSⅡelectron transport(ФPSⅡ),the maximal photochemical efficiency of PSⅡ(Fv′/Fm′),the apparent photosynthetic electron transfer rate(ETR) and the photochemistry react rate (Prate) decreased while the intercellular CO2 concentration(Ci),the initial fluorescence(F0)and the hot dissipation of antenna(Drate) increased.The index volatility of the Cymbidium goeringii ‘Songmei’ which was treated with ABA and PP333 was below that of the water and recovered quickly after the realeas of low temperature stress. These results syggested that the low temperature stress had caused damage to the PSⅡ reaction center,and the ABA and PP333 could ease the hurt of the PSⅡ reaction center and maintain both the primary capture capacity and assimilation efficiency of light energy,and the final ensure the photosynthesis capacity of Cymbidium seedlings.