An infusion needle structure of drug infusion device includes: an infusion needle including a front end and a back end; a needle holder provided with at least one auxiliary fastener; one fastening portion, arranged inside the infusion device, cooperates with the auxiliary fastener to lock the needle holder in the working position; an unlock hole provided on the needle holder or on the housing of the infusion device; and an unlock rod that is inserted into the unlock hole and pushed, thus releasing and resetting the needle holder. The infusion needle is able to reset and released when the infusion device is during replacement.

Various systems and methods for the pressure-regulated transfer of medical fluids are disclosed. The system can include an adapter assembly that connects with a medical container and with a syringe assembly. The syringe assembly can include a first reservoir and a second reservoir. In various embodiments, when the adapter assembly and the syringe assembly are coupled, the first reservoir and the container can exchange regulating fluid and the second reservoir and the container can exchange medical liquid from the medical container.