Abstract: To understand the difference of photosynthetic physiological characteristics and improve the quality of forest trees, the photosynthetic system was used to determine the photosynthetic physiological parameters and change law of artificial mutagenic cultivars, variant diploid leaflets and common diploid varieties. The results showed that the diurnal variation of net photosynthetic rate of tetraploid and diploid alpine leaves had a single peak curve, but the peak appeared at different times. The order of LSP from high to low was diploid species[1691.67μmol/(m2·s)]>variantspecies[1657.14μmol/(m2·s)]>tetraploidvarieties[1635.71μmol/(m2·s)], andtheorderofLCP fromhightolowwasvariantspecies[77.43μmol/(m2·s)]>diploidspecies[61.53μmol/(m2·s)]> tetraploid varieties [36.41 μmol/(m2 ·s)]. The order of apparent quantum yield of photosynthesis from high to low was: tetraploid species [0.0132 μmolphotons/(m2 · s)] > diploid species [0.0131 μmolphotons/(m2 · s)] > variant varieties[0.0104 μmolphotons/(m2·s)]. The order of CSP from high to low was diploid species (1371.43 μmol/mol)> variant varieties (1350 μmol/mol) > tetraploid species (1337.5 μmol/mol), and the order of CCP from high to low was variant species (153.17μmol/mol) > diploidspecies 149.48 μmol/mol) > tetrap loidvarieties (129.01μmol/mol), the order of carboxylation efficiency from high to low was diploid species(0.0194)> tetraploid species (0.0180)> variant varieties(0.0165). The leaf chlorophyll content of tetraploid species was significantly higher than that of diploid specie (P<0.05). The chlorophyll a, total chlorophyll content, carotenoid content, chlorophyll a/b, carotenoid /chlorophyll in the leaves of tetraploid species were significantly higher than those of the common diploid species and variant varieties. In conclusion, the assimilation and leaf light conversion efficiency of tetraploid species were higher than that of diploid species. The ability of tetraploid species to use weak light was better than that of diploid species, and more assimilates could be produced under weak light condition.