Potassium is an important qualityelement，in order to select the most suitable potassium content for the bestjujube fruitquality，the 5 -year-old Jun jujube trees were made as researchmaterials，different amount of potash fertilizer wasapplied during flowering stage and fruit swellingperiod，and the leaf photosynthetic parameters，fluorescence parameters and fruit quality were measured.The results showed that the effect of potash fertilizer concentration on the growth and fruit quality of Jun jujube was obvious.Within the range of potassium application of 0~153 g/plant，chlorophyll content，netphotosyntheticrate( Pn)，stomatalconductance( Gs)，transpirationrate( Tr)，photochemical quantumefficiency( Fv /Fm)，photochemical quenchingcoefficient(qP)，electron transferrate(ETR)，starchcontent，vitamin Ccontent，glucosecontent，soluble sugarcontent，soluble proteincontent，sugar -acid ratio，longitudinal and transversediameter，and single fruit weightwere all increased with the increase of potassiumcontent，and reached the peak at the potassium content of 153g/plant，butwhen potassium was applied as 153~306g/plant，they showed a downwardtrend，but the intercellular CO 2 concentration(Ci)and non -chemical quenchingcoefficient(qN)firstly decreased and then increased，and these two parameters had the lowest value at 153g/plant potassium.The photochemicalefficiency(PSII)was the highest at 229 .5 g/plant potassium.Theresults of principal component analysis showed that among the five potassium applicationlevels，the 153 g/plant K 2O was the best for improving fruit quality and leaf photosynthesis.Insummary，potassium fertilizer improved fruit quality by increasingchlorophyll content in leaves and improving the function of photosynthetic organs of Jun jujube，and 153 g/plant K 2O by furrow application was the best.