The objective of this study is to explore the relationship between lipid biosynthesis and expression of source and sink genes during Camellia oleifera seed development. The line “MY003” with high oil content in the seeds and the line “MY008” with low oil content in the seeds were selected as sample trees. These seeds were harvested at June 2, July 4, August 5, and September 3. The oil contents in the seeds were determined by the method of chloroform methanol. The differential expression of source gene (GPD1) and sink genes (DGAT1 and DGAT2) involved in lipid biosynthesis between high and low oil content lines were determined using qRTPCR, and the effects of these three genes on lipid biosynthesis and accumulation were analyzed. The results showed that: (1) the oil contents in the seeds of two lines were in a gradual upward trend (0.16%-24.1%), and it began to rise rapidly after July 4. The oil contents in the seeds of “MY003” were higher than that of “MY008” at all stages; (2) The peak values of GPD1, DGAT1 and DGAT2 expression in the seeds of “MY003” were significantly higher than that of “MY008” during seed development. The expression of DGAT1 and DGAT2 still appeared peak values after the high level expression of GPD1, but the peaks of GPD1 gene appeared in the early period of seed development, and the peaks of DGAT1 and DGAT2 genes appeared in the later period of seed development. The high expression of source gene GPD1 contributed to promote the TAG precursor G3P high synthesis efficiency in the early of seed development, and the high expression of sink genes DGAT1 and DGAT accelerated high TAG accumulation in later period of seed development. There were positively correlated relationships in expressions among GPD1, DGAT1 and DGAT genes. Thus, the coordinated expression of source gene GPD1 and sink genes DGAT1 and DGAT2 resulted in the lipid biosynthesis and accumulation in C. oleifera seeds. These results could provide scientific bases for studying on molecular mechanism of lipid biosynthesis in the seeds of C. oleifera.