Abstract: 【Objective】 To explore the effects of planting density on canopy structure and microclimate of winter wheat in walnut-wheat intercropping pattern. 【Method】 In 2016-2017, planting densities of 4.5 million plants /hm² (M₁), 5.25 million plants /hm² (M₂), 6 million plants /hm² (M₃), 6.75 million plants /hm² (M₄) and 7.5 million plants /hm² (M₅) were set in walnut-wheat intercropping fields and canopy structure, canopy air temperature, humidity and canopy light transmittance of winter wheat were observed. 【Result】 The results showed that the single leaf area, plant height and stem diameter of winter wheat in the distal crown region were higher than those in the lower crown region. With the increase of planting density, the leaf area, internode length and internode roughness of winter wheat in the subcrown and distal crown showed a trend of "first increasing and then decreasing", and the plant height varied from 76.49-81.66 cm (subcrown) to 78.34-86.27 cm (distal crown). The air temperature in the lower canopy area and the far canopy area showed a curve of "first rising and then falling". The M₁ treatment in the lower canopy area was the highest, while the M₄ and M₅ treatment in the far canopy area were relatively high. The humidity in the far canopy area decreased slowly in the morning and rose slowly in the afternoon, and the humidity trough lasted for a short period. The variation amplitude of the canopy air humidity in the lower canopy area (44.73%-100%) was higher than that in the far canopy area (36.62%-100%).The incidence photosynthetic effective radiation (PAR) at the top of wheat canopy was significantly lower than that in the far canopy. The photosynthetic effective radiation interception (IPAR) of the canopy in the lower and far canopy areas showed a trend of "first rise and then fall" with the increase of density, and reached the maximum value in M₂ treatment. 【Conclusion】 It was concluded that the canopy structure and microclimate of winter wheat in walnut-wheat intercropping were more suitable when the planting density was 5.25 million plants /hm².