Abstract: Based on field observations and following the geometric properties of the canopy of paulownia and principle of polar radiation transfer inside the canopy,a variety of patterns are simulated of solar irradiance distribution in fields with crop-paulownia intercropping of various structures under clear and overcast skies,and the shift of the tree shade is investigated.Results show that under the condition of the paulownia lined in the S-N direction with a 5m specing between trees the optimal structure of the intercropping is formed on the basis of the growth of the tree row spacing from 10 to 40m as a function of the continued operation.Simulations also indicate that the highest yields and hence economic benefits are gained after a 6-year intercropping with the row spacing of 40m.