A needle-replaceable and self-destroying insulin syringe comprises a barrel (1), a push rod (2), a rubber piston (3) and a needle seat (4). The barrel (1) is provided with a connection needle seat (7) cooperating with a needle hub (5). The connection needle seat (7) is supported and fixed at a front end of the barrel by a support seat (8). The needle hub (5) extends downwards to form a fixing ring (9). A snap ring (10) is formed at an upper end of the connection needle seat (7). The snap ring (10) protrudes into a bore of the fixing ring (9) and snap-fitted with the fixing ring (9). A large groove (13) is provided in a wall of the bore of the connection needle seat (7). An upper end of the support seat (8) protrudes into the bore of the connection needle seat (7). First elastic detents (14) are formed at the upper end of the support seat (8) and come together towards the center. A ring of flange (15) is provided at the outside of the upper end of the support seat, and seats in the large groove (13), capable of sliding up and down along the large groove (13). First elastic support pawls (16) are formed at a lower end of the connection needle seat (7), and the inner wall of the barrel is correspondingly provided with a small groove (17) in which the first elastic support pawls (16) can be embedded. A ring of flange shoulder (18) is provided at the outside of the lower end of the support seat, and abuts against the first elastic support pawls (16).
