The invention provides an improved secondary waterproof joint for a W-type immersed tunnel and belongs to the technical field of engineering testing. The improved secondary waterproof joint comprises a GINA waterstop, an A-type end steel shell, a B-type end steel shell, a W-type waterstop, a GINA waterstop pressing plate, a water stopping steel disc, a W-type waterstop pressing plate and a pressing sheet, wherein the A-type end steel shell and the B-type end steel shell are fixedly connected with a top plate or a bottom plate through concrete; one segment of the GINA waterstop is fixed to the B-type end steel shell; the GINA waterstop pressing plate is fixedly connected with the A-type end steel shell and compacts the other end of the GINA waterstop; the water stopping steel disc is embedded in the concrete and connected with the A-type end steel shell and the B-type end steel shell; a stud penetrates through the W-type waterstop pressing plate and fixes the W-type waterstop pressing plate; the W-type waterstop is fixed to the W-type waterstop pressing plate through the pressing sheet. The flexible joint for the immersed tunnel has a good water stopping effect, and damage, caused by axial, vertical and horizontal displacement produced during long-term operation of the tunnel, to the flexible joint can be effectively reduced.