Disclosed is a connection structure between a needle seat and a syringe in a safe injector. The front end of the syringe (1) is provided with a connection cylinder (1a) with a slightly smaller outer diameter than the syringe (1), the needle seat (2) is columnar and the front end of the needle seat (2) is used to connect a needle (3). The connection structure comprises an elastic connection piece (2a) at the back end of the needle seat (2) and a connection portion 1 (1a1) inside the connection cylinder (1a), wherein a connection portion 2 (2a1) is provided outside the connection piece (2a). The connection cylinder (1a) is sheathed on the needle seat (2). An expansion member (5) is located at the connection piece (2a), wherein the expansion member (5) abuts inside the connection piece (2a) and allows the outer side of the connection piece (2a) to expand to be in contact with the inner side of the connection cylinder (1a). Under the expansion effect of the expansion member (5), the above-mentioned connection portion 1 (1a1) and the connection portion 2 (2a1) are in a snap-fit connection. The connection structure has a high stability and a simple structure.
