A linear actuator includes a back fixture formed of a first part (1), a second part (2), and a plastic bearing (3), the first part (1) connecting with the second part (2), grooves are disposed inside the first part and the second part, and connection structures are disposed outside the plastic bearing (3). The plastic bearing (3) is secured inside the first part (1) and the second part (2) with the grooves and connection structures. The back fixture can be directly fitted onto a bed frame by applying a certain force to make an elastic deformation of this back fixture, thereby accelerating the installation of the actuator. This not only significantly reduces the noise caused by the connecting portion during the operation of the actuator, but also reduces the wearing of connecting parts, thereby significantly extending maintenance-free life.