Rare and endangered M.oleifera seeds dried in shade after peel removal are used as materials, stratification treatment in greenhouse sand pond, different germination stages from stratification treatment to cotyledon excavation, we investigated the change characteristics of seed development morphology, storage material accumulation, enzyme activity and seedling type of M.oleifera, to understand the causes of seed dormancy. The results showed that: (1) it takes about 195 days for M. oleifera seed to germinate and form seedlings from the beginning of dormancy release. It takes about 75 days for the morphological development of young embryo to ripen, and then 30 days later is the period when the seeds germinate intensively, with the highest germination rate. This process can be divided into 7 stages (S1-S7 stages) according to the characteristics of the developmental morphology of the embryo: The seeds do not germinate at S1 stage; S2 stage seed embryo “exposed”; At S3 stage, the radicle breaks through the seed coat more than 1 cm long; At S4 stage, the junction between hypocotyl and radicle forms a hooked structure; The formation of “S” type embryo and the enlargement of the front end of radicle at S5 stage; At S6 stage, the seeds not only have enlarged radicles, but also have lateral roots; At S7 stage, cotyledons fall off, germ unearthed and true leaves appear. (2) M.oleifera seeds in the process of wet sand stratification, seed embryos length and embryo rate increased from (5.49±1.57) mm and (19.48±5.72)% during stratification at S1 stage to (67.92±2.94) mm and (240.75±15.29)% at S6 stage, the embryo rate increased by 12.4 times on average. It shows that the embryo of M. oleifera seeds needs to go through the post-ripening process to germinate, which belongs to the post-embryonic type seeds. (3) From the perspective of seed physiological indicators, with the increase of wet sand stratification time, soluble protein content and starch content in seed embryo decreased first and then increased, while the contents of soluble sugar and malondialdehyde (MDA), and the activities of superoxide dismutase (SOD) and peroxidase (POD) increased first and then decreased; However, the size and shape of endosperm did not change significantly at the same time, the contents of starch, soluble sugar, soluble protein, and the activities of SOD and POD showed a general downward trend. (4) The percentage of embryo and germination of seeds were negatively correlated with the contents of soluble protein and starch in endosperm, there was a very significant positive correlation with soluble sugar content (P<0.01). The study found that, M. oleifera seed undergoes a series of physiological and biochemical changes from dormancy release to germination, degradation and enzymatic activity of macromolecules including soluble proteins in the endosperm where nutrients are stored. It provides material and energy for the completion of post-ripening of seed embryos, releasing dormancy and entering germination. The physiological change process and the morphological development process of seed embryos cooperate with each other to complete the germination of M. oleifera seeds. Seedlings have completed germination to form original cotyledon-shaped seedlings, the cotyledons only have the function of absorbing nutrients but not assimilating.