With three panicle types of rice varieties and hybrids in Liaoning as entries, the effects of spacing of Japonica rice on light interception capacity, population light distribution, light conversion efficiency at full heading stage and yield were studied. The results showed that the leaf area indices at full heading stage, closely related to light interception, increased first and then decreased with the decrease of transplanting density. The extinction coefficient in one day increased first and then decreased, and the K value increased with the increase of planting density. Yield was positively correlated with canopy extinction coefficient and inclinations of the upper three leaves. In terms of energy efficiency, the yields were positively correlated to flag leaf stomatal conductance, intercellular CO2 concentration and transpiration rate. At the configuration of high (15 cm x 25 cm) and low (20 cm x 30 cm and 20 cm x 35 cm) densities, Japonica rice could increase light interception capability and optical conversion efficiency, but could not obtain high and stable yields due to limitation by lodging and panicles of per unit area, respectively. At the configurations of 15 cm x 30 cm and 20 cm x 25 cm, it was easy to get adequate panicles, optimize the structure of the canopy, reduce lodging risk, and obtain high yield.