The invention discloses an AAV carrier for treating type 2 diabetes and a preparing method and application thereof. The AAV carrier is obtained by inserting GLP-1 gene between cleavage sites of a multiple cloning site of a pAAV-MCS carrier, wherein the sequence of the GLP-1 gene is shown in SEQ ID NO:1 in the sequence table. The AAV carrier has a wide host range and low immunogenicity. The AAV carrier is low in pathogenicity and high in safety, and can hardly cause insertion mutation. Meanwhile, exogenous gene GLP-1 expression time is long, expression stability is high, and type 2 diabetes can be effectively treated. The production technology of the AAV carrier is perfect, and large-scale production can be conducted.