Abstract: The response of tree-ring structure to the variation of average monthly temperature and precipitation on Populus simonii and P.×beijingensis collected from the Mu Us Desert, Inner Mongolia, was studied using dendrochronology techniques. The results showed: the patterns of variation in the RW (ring width) index of P. beijingensis was similar to that of P.×beijingensis, while the range of variation of the former was bigger than that of latter. This coincides with the big climate variation in the Mu Us Desert. The response model built up with monthly average temperature and precipitation could explain 46% to 55% of RW and VLD (vessel lumen diameter) variation. The variation of RW and VLD of P. beijingensis had a similar response to average monthly temperatures and precipitation. Too high temperatures in February would restrain the increment both in RW and VLD, while the precipitation and temperature in summer could accelerate evidently an increment in RW and VLD. Responses of RW of P.×beijingensis to average monthly temperature and precipitation did not quite agree with that of VLD, and neither RW nor VLD had significant responses to climate change.