Endomorphins,with high analgesic activity and fewer undesirable side effects,are not in clinical use because of the blood-brain barrier(BBB).To overcome the BBB and improve brain uptake of neuropeptides,various strategies have been developed to attain the most appropriate receptor binding affinity and high permeability of BBB [1-2].One promising solution is to use cell-penetrating peptides(CPPs).CPPs have ability to translocate cell membranes and have been successfully applied for delivery of therapeutic molecules across BBB [3-5].Most of articles before focused on the selection of efficient CPPs and expansion range of transport molecules,but little was known about the transport efficiency of different conjugation types between cargo and CPPs.