Abstract: On the basis of field observation and with the principles and methods of agricultural meteorology,the daily variations of the shadow width of jujube tree belts and the relative light intensity were analyzed in the jujube—wheat interplanting system,and the characteristics of vertical distribution of the light within the wheat canopy inside and outside the shadow were studied. The sunshine vertical distribution curves in the wheat canopy inside and outside the shadow were simulated by mathematical methods. The results showed that the shadow area of the south north planting jujube tree belts was fairly wider,but the relative light illuminance was larger in early morning and late afternoon than at about noon.Although the sunshine vertical distribution in the wheat canopy inside and outside the shadow was obviously different,they both observed the decreasing law for Gauss Curve.