Abstract: The research results showed that the wheat yield was determined by Colony Growth Rate(CGR).At the level of 4t/hm2 grain yield of wheat in annual three-crop system the average CGR showed 8.9g/(m2·d),the greatest Leaf Area Index (LAI) arrived 5.1─5.2 and the aver-age Net Assimilation Rate(NAR) of growth period appeared 3.6g(m2 ·d).In the condition with the average annual Solar Radiation(S)100J/(cm2·d),the Light Energy Utilization Rate (Eu) of wheat arrived 1.45%.The results of multiple correlation analysis showed that during wheat growth period the LAI appeared extremely significant positive correlation to CGR.In the high grain yielding colony with the most suitable LAI, the NAR was the decisive factor to CGR.From booting stage to yellow mature the photo- productoin was restricted by S.In Southern China re-gions, after booting stage, the S appeared fluctuating significantly according to the coming dura-tion and raining situation of the spring rain in different years, which make up the variable yields in different years.