The invention relates to a method for preparing a porous fiber from natural polymers and a product and application thereof. The preparation method includes the following steps that 1, a natural polymer solution for spinning is prepared; 2, the natural polymer solution is subjected to solution spinning, directional freezing is conducted at the time of spinning, and fiber is collected; 3, the fiberis freeze-dried to remove ice crystals, and the porous fiber with an oriented pore structure is obtained. Through the combination of directional freezing and solution spinning, the obtained porous fiber has the oriented pore structure, and the method can be widely used for preparing porous fiber materials from different kinds of natural polymers.