The spatial and temporal variations of all components of heat balance in a paulownia-crop field are examined in detail using actual measurements. Results show that in such a field anda control plot the latent heat flux(LE) remains predominant,sensible heat flux(H) is less than LE but higher than Q_s(soil heat flux);all components inside such an intercropped field are smaller as compared to the control plot but LE and Q_s account for a higher proportion in net radiation(R_n);the tree belt has its effect on the components dependent on the intercropping structure andmeasuring site. Finally, water use efficiency(WUE) is computed of wheat and cotton in the intercropping and the value is found to depend on the variety and its growth duration and to belower in the control plot.