The effects of the film mulching on the transportation and distribution of the pre-stored carbon 14C-reserves in the grain filling stage was studied with the techniques of feeding labelled 14CO2 to flag leaves and isotope tracing. The results showed that about 90 percent of the assimilated 14C-reserves before anthesis had been stored in the stem, sheath and rachis, and about 10 percent remained in the leaves at anthesis. Both of them will be transported to the kernels. When maturation, 14C-reserves in the leaves were almost exported entirely, about 65% 14C-reserves remained in the stem, sheath and rachis, and about 30-35% stored in the kernels. For the wheat with the film mulching treatment the 14C-reserves were transported in a slower speed than that in the control. The investigation also revealed that under the film mulching conditions, the wheat had a larger leaf area with a slower senescence speed and a stronger assimilatory power, accumulated more dry matter andhigh yield. It was concluded that the main cause of the kernel production increase under the film mulching were the faster growth in the early stage and the slower senescence in the later stage, hence with a larger green leaf area and a stronger assimilatory power leading to the total assimilated dry matter content increased greatly and the production increased similarly, Whereas this didn’t result from the increase of assimilates translocation and distribution to the kernels .