Abstract: In the report, in order to understand the correlation among photosynthetic physiological characteristics and environmental factors of different species of Pandanus amaryllifolius Roxb, the LI-6400 XT photosynthesis system was used to determine the photosynthetic diurnal variation of different species of P. amaryllifolius under natural environmental conditions for breeding and scientific cultivation provide a theoretical basis. The results showed that the net photosynthetic rate（Pn）, transpiration rate（Tr）, and stomatal conductance（Gs） of the different species show a single-peak curve, and the Pn, Tr, and Gs values of Pandanus sp are higher than P. amaryllifolius, the Pn and Gs values of Pandanus sp reached the highest values are 12.98 μmol·m^-2·s^-1 and 0.41 μmol·m^-2·s^-1 at 13:00, while P. amaryllifolius reached the highest values are 5.55 μmol·m^-2·s^-1 and 0.11 μmol·m^-2·s^-1 at 11: 00, both of which reached the highest value at 13:00, and Pandanus sp was 3.37 μmol·m^-2·s^-1, P. amaryllifolius showed 1.47 μmol·m^-2·s^-1, and there was a significant positive correlation between Pn of both and Tr and Gs; the daily variation of water use efficiency（WUE） of Pandanus sp showed a downward trend, P. amaryllifolius firstly increased and then decreased. The WUE value of P. amaryllifolius continued to rise, reaching a maximum value of 4.96 μmol·m^-2·s^-1 at 15:00, and which were higher than that of the Pandanus sp, there was a significant positive correlation between the WUE of P. amaryllifolius and Pn, while there was no correlation between the WUE of Pandanus sp and Pn. The diurnal variation of CO₂ content（Ci） in Pandanus sp showed an increasing trend, P. amaryllifolius increased firstly, then decreased and then increased, both rose to the highest value at 19:00, and P. amaryllifolius was 561.04 μmol·m^-2·s^-1, Pandanus sp was 378.15 μmol·m^-2·s^-1; The daily variation of the stomata prevention value（SLR） of the P.sp showed a decreasing trend, P. amaryllifoliusfirst decreased and then increased after decreased, the SLR value of P. amaryllifolius firstly increased and then decreased, reaching a maximum value of 0.37 μmol·m^-2·s^-1 at 15:00, the SLR values of P. amaryllifolius were higher than that of Pandanus sp from 13:00 to 17:00. Additionally, there was a significant positive correlation between the relative humidity（RH-H） in the environmental factors and Pn, while there was a significant negative correlation between atmospheric CO₂ concentration（Ca） and Pn. In summary, P. amaryllifolius is suitable for planting in a humid and ventilated environment. Although Pandanus sp has stronger photosynthetic capacity than P. amaryllifolius, the water use efficiency and growth potential of P. amaryllifolius are stronger than that of the Pandanus sp.