The invention discloses a preparation method and a use method of a Terminalia catappa seed initiator. According to the invention, lauryl sodium sulfate and copper chloride are introduced into a PEG and sodium chloride solution; the preparation parameters are strictly controlled, the spatial conformation of PEG is influenced, and the initiator which can effectively shorten the germination time of the Terminalia catappa seeds, improve the germination rate and realize synchronous germination of the seeds on the basis of only partially removing endocarp is successfully obtained. By the adoption ofthe method, the average germination time of the Terminalia catappa seeds is shortened by 44% or above, the germination rate is increased by 47% or above, and the synchronization index is increased by19% or above.