The Hangjinqi block, abundant in block in natural gas resources, has been plagued by severe issues of well leakage and wellbore instability due to its intricate geological attributes. This study focused on investigating the reservoir protection performance and mechanism of polyamine drilling fluid were studied. The swelling inhibition capabilities were investigated by expansion experiments, hot rolling tests and capillary force assessments. The shielding and temporary plugging performance of polyamine drilling fluid was investigated by simulating the intrusion of polyamine drilling fluid in fractures and acid dissolution plugging experiments. The findings revealed that the inhibition performance of polyamine drilling fluid was mainly caused by the single agent of amine inhibitors, nano-emulsion and micelle polyether. These agents impeded the interaction between water molecules and the formation from diverse perspectives, thereby diminishing the extent of swelling. Secondly, the low specific gravity of the polyamine drilling fluid enabled drilling under low pressure differentials, facilitating the creation of a shielding temporary plugging effect. That was characterized by the formation of a thin, compact filter cake on the fracture end face, effectively curtailing the penetration depth on the drilling fluid and thereby mitigating its detrimental impact on the reservoir and enhancing fracture conductivity. Thirdly, the study demonstrated that polyamine drilling fluids exhibited favorable natural flowback behavior within fractures and possessed substantial acid dissolution potential, capable of restoring fracture permeability to levels surpassing 80%. The research results are of great significance to the exploration and development of tight sandstone gas reservoirs.