A delivery system of a portable delivery device, using a chamber with three connections structure (10) arranged on the upper housing (1) as a buffer channel for the flow passage of the drug fluid from the external syringe into the reservoir (6) and from the reservoir (6) into the infusion needle； and the structures on the upper, the lower housings (1), (4) and the needle seat (2) accommodating the infusion needle mate with each other sophisticatedly ensuring the compactness of the delivery device and enabling the patient to control the position of the infusion needle safely and conveniently at the same time； in additional, the needle seat cover (7, 8) which covers the needle seat (2) enhances the safety of using the infusion needle. The delivery system of a portable delivery device has advantages of small size, sophisticated structure, simple operation, safety guarantee.
