Abstract: To determine the response of water and carbon fluxes to biological and abiotic factors at different growth stages of flue-cured tobacco and further to analyze the temporal sensitivity of variation of water and carbon fluxes, the diurnal variation characteristics in typical flue-cured tobacco fields in Panzhihua-Xichang (Pan-xi) were studied at different growth stages of flue-cured tobacco based on the eddy covariance data. The asymmetric response to time in variation of water and carbon fluxes was measured according to canopy conductance, atmospheric temperature, vapor pressure difference (VPD) and net radiation. The results showed that except for seedling and maturity Ⅲ stages, the variation of both CO₂ flux and evapotranspiration (ET) presented a bimodal curve during a day at the other tobacco growing stages, which became slightly decline or slowdown from 11:00 to 13:00. At the same net radiation intensity, the values of CO₂ flux and ET in the afternoon were significantly higher than those in the morning, which was contrary to canopy conductance. In the morning, lower temperatures and VPD inhibited the positive regulation effects of canopy conductance and net radiation on water and carbon exchange. However, in the afternoon, higher temperature and VPD compensated the effects of decrease of canopy conductance and net radiation on water and carbon exchange. Therefore, the diurnally non-synchronous variations of temperature, VPD and net radiation were found to be the main external factors causing the diurnally asymmetric response of water and carbon fluxes in tobacco fields.