Aims Our objective was to study two widely planted hybrid poplars,Populus deltaids 'cv-64' (P64) and P. simonii canaden × P. russkii-9 (Jia),to explore their growth mechanisms and the solar energy utilization by photosystem II (PSII) antennae to thermal energy dissipation and photosyn-thetic electron transport characteristics during long-term adaptation to the ambient environment. Methods We studied energy utilization by computing chlorophyll fluorescence parameters and photo-synthesis. Plants were grown at the Plain Forest Farm Nursery of the State Forestry Bureau of Ili Autonomous Prefecture in China's Xinjiang region. Important findings The diurnal changes of net photosynthesis (Pn) were bimodal and had a 20.1% gap under high photon flux density (PFD). The actual efficiency of open PSII centers (ΦPSII) were all of the "U" type,and their average values were equal. The ΦPSII of P64 and Jia reached the minimum value at 16:30 and 14:30,respectively. The closure value had one wave hollow at 14:30,and there was no significant difference (p0.05) in whole-day average values. The non-photochemical quenching co-efficients (NPQ) all achieved the maximum value at 16:30. Jia's NPQ maximum was less than that of P64,and the whole-day NPQ difference reached 31.7%. The estimated rates of photochemistry (E.P) and non-photochemistry (E.D) showed that under the lower PFD the poplars used more than 50% of theabsorbed solar energy for the photochemical quenching,and under high PFD the absorbed solar energy for P64 for the photochemical quenching is greater than the proportion for Jia,while the absorbed solar energy for P64 for heat dissipation is less than the proportion for Jia. The E.P had no difference and reached the maximum estimated value when its E.D reached the maximum. P64 tended to use more ab-sorbed solar energy for photochemical quenching,but Jia tended to use more solar energy for non-photochemical quenching. The cumulative values and average values of the Pn for Jia were much larger than values for P64,but the absorbed solar energy of P64 is greater than the proportion of Jia for the photochemical quenching. These results prove that it is inadequate to calculate the absorbed energy only by the chloroplast fluorescent characteristics of light received.