Abstract: After being sprayed with different concentration ALA for 4 days, photosynthesis parameters of 2 a jackfruit tree were analyzed with a LI-6400 portable photosynthesis system analyzer to study the effect of ALA on photosynthetic physiology in jiackfruit. The results showed that low concentrations of ALA could significantly promote jackfruit tree photosynthesis, in which, the Pn, Tr, WUE , Gs, Ci of 10 mg/L ALA respectively increased 56.0%, 30.6%, 19.4%, 23.8%, 54.2% than CK,Ls reduced 37.6%. But thePn, Tr, Gs, Ci of 20 mg/L were respectively reduced 2.2%, 28.4%, 31.1%, 11.6% than CK, and theWUE, Ls increased by 36.3%, 8.1%. Thus it can be seen appropriate concentration of ALA can be effectively enhance the jackfruit photosynthesis, but the high concentration not.