We provided a gene pool of moderate size for selecting or manipulating the candidate genes that favour the acquisition of seed dormancy, shedding light on the elevation of seed oil content in oilseed rape by blocking lipid degradation in developing seeds. In oilseed rape, the association between the germination potential of premature seeds and the final level of seed lipids, and the underlying mechanism, is elusive. Here, we investigated phenotypic differences in the germination percentage of premature seeds in a collection of oilseed rape cultivars. We compared the dynamic lipid accumulation between the deep-, moderate- and non-dormant genotypes and compared the transcriptomes of the seeds at 40 days after pollination between multiple pairs of deep- and non-dormant genotypes. We identified a wide range of differences in germination percentage of premature seeds and the association between the germination potential and the change of fatty acid content at late stage of seed maturation. The comparisons of transcriptomes between deep- and non-dormant seeds revealed the genetic basis for the dormant difference, e.g. the different expression levels of the genes involved in gibberellic and abscisic acid biosynthesis and/or signalling, fatty acid metabolic pathways, and the structure of seed cell wall. We provided a gene pool of moderate size for selecting or manipulating the candidate genes that favour the acquisition of seed dormancy, shedding light on the elevation of seed oil content in oilseed rape by blocking lipid degradation in developing seeds.