The invention provides a polypropylene elastic fiber, in which the components consist of (mass %) 90-10% fiber-grade isotactic polypropylene and 10-90 % intertactic polypropylene and the spin-grade polypropylene blending resin is prepared by performing intimate mixing to the said components and squeezing, casting and pelleting with twin-screw extruder at 170-200 DEG C. The 0.5-10.0dtex polypropylene fiber for industrial purpose and civil can be prepared by melt spinning in common spinning apparatus. The advantage is that the rebound elasticity is more excellent than isotactic polypropylene, compared with the traditional elastic body, it has better dynamic property and expands the usage and end use field of the common polypropylene fiber.