Objective The aim was to elucidate the effects of N rates on rice canopy microclimate and community health so as to provide a sci- entific basis for studying the production potential in irrigated rice with healthy canopy. Method The effects of rice population structure traits under different N rates on rice canopy temperature, relative humidity （ RH）, light transmittance and sheath blight were studied by using Sunscan canopy analysis system and HOBO（ Pro Temp/RH IS logger）. Result The results showed that leaf area index, plant height and tiller number had significant effects on canopy cooling, RH enhancing and light reducing. Extremely significant multiple linear regression relationships existed among canopy day temperature, day RH, LAI and tiller number, and among light transmittance, tiller number and plant height. At flowering stage, per unit LAI could result in a day-maximum-temperature （Tmax） deceasing of 0.87℃ and a day-minimum-RH （RHmin） enhancing of 2.5% within canopy. Similarly, 100 plants per ms could respectively cause a Tmax deceasing of 1.23℃ and an RHmin enhancing of 3.3% in rice canopy. And per 10 cm plant height and 100 plants per m^2 could respectively reduce 9.3% and 7.8% of light in canopy. Conclusion Sheath blight disease index was significantly enhanced as the canopy day temperature decreased, day RH increased and light transmittance reduced. Bigger canopy from higher nitrogen level treatment leads to a more stable canopy microclimate with little changes in temperature and RH during day and night, which has the risk of worsening canopy health. Thus, moderately controlling the space development of canopy is the basis of constructing healthy canopy in rice.
