Sulfur is a promising cathode material with a high theoretical capacity of 1672 mAh g-1, however, the practical energy density of Li-S battery is far away from such promising due to its low active material utilization and low sulfur loading. Moreover, the challenges of the low electrical conductivity of sulfur and the high solubility of polysulfide intermediates still hinder its practical application. Here, we report a kind of free-standing and foldable cathodes consisting of 3D activated carbon fiber matrix and sulfur cathode. The 3D activated carbon fiber matrix (ACFC) has continuous conductive framework and sufficient internal space to provide a long-distance and continuous high-speed electron pathway. It also gives a very larger internal space and tortuous cathode region to ACFC accommodate a highly sulfur loading and keeps polysulfide within the cathode. The unique structured 3D foldable sulfur cathode using a foldable ACFC as matrix delivers a reversible capacity of about 979 mAh g-1 at 0.2C, a capacity retention of 98% after 100 cycles, and 0.02% capacity attenuation per cycle. Even at an areal capacity of 6 mAh cm-2, which is 2 times higher than the values of Li-ion battery, it still maintains an excellent rate capability and cycling performance.