Abstract: The article selected Populus tomentosa as tested material, perforation dyeing method was used to dye the wood, acid brilliant scarlet GR as the dyestuff, thermal dissipation probe (TDP) and Li-6400 photosynthesis system were applied to measure the sap flow during dyeing and monitor the changes in photosynthesis, respectively. The results showed that the direction of transport and penetration of the dye in trunk presented two-way. In the above dyeing hole, the ΔL^* value increased and ΔE^*, Δa^*, Δb^* decreased gradually with the increase of dyeing height. In the lower part of the dyeing hole, ΔE^* decrease gradually with the decrease of dyeing height. Sap flow velocity went down gradually under the influence of the dye, and the net photosynthetic rate, stomatal conductance and transpiration rate also gradually decreased.