This multi-functional extendable storage sofa bed is made of interwoven natural cotton and cotton linen fabric, delivering silky, mild and skin-friendly touch with anti-pilling, wear-resistant and breathable features. The fabric adopts a double-layer thickened zipper detachable and washable design, which resists deformation after machine washing for easy daily cleaning and long service life. The whole frame is constructed with thickened carbon steel bed frame featuring strong load-bearing capacity, paired with silent and smooth load-bearing casters for effortless pushing, pulling and retracting to switch forms flexibly. When fully unfolded, it reaches a size close to a double bed to meet the demand of temporary overnight rest. The side base material adopts eco-friendly multi-layer solid wood board with solid wood veneer craft, safe and environmentally friendly. The seat cushion is filled with high-resilience sponge with moderate softness and hardness and quick rebound, resisting sagging after long-time sitting and providing quiet, full and well-shaped sitting experience. The backrest and soft cushions are fully stuffed with sufficient PP cotton to offer adequate support, closely fitting the body curves of head, waist, back and hips to create an enveloping soft sitting feeling that relieves whole-body fatigue after long hours of use. Storage fabric bags are equipped on the side armrests, and a large-capacity hidden storage compartment is built under the sofa to store quilts, clothes and various household sundries, realizing both storage and rest functions in one piece of furniture. It supports free switching among multiple modes including standard sofa, semi-reclining and fully flat bed, and can be placed easily even in small-sized apartments, serving as space-saving multi-functional home furniture.