In order to investigate the photosynthetic characteristics and the effects between the main environmental factors and photosynthesis during florescence and fruit period of Sapindus mukorossi,we selected the florescence and fruit period to measure photosynthetic and eco-physiological characteristics of 8-year-old S.mukorossi using a portable Li-6400 Photosynthesis System(Made in USA) on sunny days.The parameters we measured were net photosynthetic rate(Pⁿ),transpiration rate(T^r),stomatal conductance(G^s),intercellular CO² concentration(Cⁱ),photosynthetically active radiation(PAR),relative air humidity(RH) and air CO² concentration(C^a).The results showed that:(1)The diurnal change of Pⁿ and T^r had a bimodal pattern(M type curve) and had a clear midday.The first and second peaks appeared at about 10:00 and about 14:00,respectively.(2)The daily averages of Pⁿ,T^r,G^s and WUE during the florescence were higher than that in the fruit period.However,the daily average of Cⁱ in the fruit period was higher than that in the florescence stage.(3)During 8:00~14:00,the daily averages of LUE in the fruit period was higher than that in the florescence stage,and the peak appeared at about 10:00,but during 14:00~18:00,that was opposite.(4)Pⁿ was significantly positively correlated with T^r,G^s and PAR,and had the closest relationship with PAR,but significantly negatively correlated with Cⁱ,and negatively correlated with C^a.(5)The main physiological factors affecting the characteristic of Pⁿ of S.mukorossi were G^s and T^r,while,Cⁱ was the main limiting factor;the main ecological factor was RH,T^a was the limiting factor and G^s was the key factor which affected Pⁿ.The results indicated that S.mukorossi adapt strongly to high-light’s capability,and it is a heliphilous plant.It is in order to guide oriented cultivation of plantation and also to manage florescence and fruit period of S.mukorossi,scientifically.