The invention provides a novel elastic fiber and a preparation method thereof. The novel elastic fiber is a two-component parallel composite fiber. In the cross section of the fiber, two parallel components are both in the shape of a round or an oval, and the two rounds or the two ovals are in tangent connection or in external connection. The novel elastic fiber is obtained by spinning two types of polyester chips, due to the fact that the shrinkage stress of the two fibers is different, different shrinkage effects are generated, the novel elastic fiber is made to have crimp elasticity very similar to that of natural wool, and therefore the novel elastic fiber has good elasticity. Large-scale production of the novel elastic fiber can be achieved, and meanwhile the production cost is lowered.