The invention provides a forklift three-stage full-freedom portal assembly. Roller trains for relative sliding are arranged between an outer portal and a middle portal, between the middle portal and an inner portal and between the inner portal and a forklift frame respectively. Two rear hoisting oil cylinders are symmetrically and fixedly arranged on the outer portal. Piston rods of the rear hoisting oil cylinders are both connected with the middle portal. A rear chain wheel is fixedly arranged on the middle portal. The two ends of a rear cylinder chain wound around the rear chain wheel are fixedly connected with the outer portal and the inner portal respectively. A front hoisting oil cylinder is fixedly arranged on the inner portal. The top end of the front hoisting oil cylinder is fixedly provided with a front chain wheel. The two ends of a front cylinder chain wound around the front chain wheel are fixedly connected with the inner portal and the forklift frame respectively. The portal assembly is compact in overall structure, the size of the front overhang part is reduced by 8%, strength and rigidity of the portal assembly are improved, and force is transversely and longitudinally exerted on the portal assembly in a balanced mode during hoisting; main idler wheels and side idler wheels are distributed reasonably, shaking and deformation are eliminated after the portals conduct hoisting, and high-place work safety of the portals is improved; stability during work of a forklift is greatly improved.