Abstract: OBJECTIVE To study on the effectiveness and safety of the colloid-core flexible nano-liposomes (FNLs) mediated protein drugs by pulmonary drug delivery. METHODS FNLs were prepared by the injection method combined with emulsion technology, physiochemical properties of FNLs were detected by the method of preparation. Intratracheal instillation of insulin-FNLs was performed to evaluated hypoglycemic effect. FITC administered in accordance with the intratracheal instillation into the lungs, to estimate the FITC-FNLs deposition ratio. Histological changes in the lung were also observed to evaluate the safety of FNLs by hematoxylin and eosin. RESULTS FNLs showed satisfied elliptic morphology, with average particle size (153±0.94)nm, Zeta potential-(20.9±0.21)mV. FNLs promoted insulin pulmonary absorption effectively and showed good relative pharmacological bioavailability, to achieve a significant hypoglycemic effect, the minimum reductions of the blood glucose concentration reached (18.25±4.19)%; FNLs could be increased drug deposition in the lungs to promote drug into the systemic circulation, and better tolerance in the lungs. CONCLUSION FNLs as pulmonary drug delivery system, can be overcome intrapulmonary absorption barrier by the pulmonary administration of protein drugs, increased bioavailability, lay the foundation for development of pulmonary drug delivery system.