The invention provides a low-cost high-performance large-tow carbon fiber spreading device. The low-cost high-performance large-tow carbon fiber spreading device comprises a yarn placing device used for placing of fiber bundles and achieving tension control and is characterized in that after the fiber bundles are led out from the yarn placing device, the fiber bundles enter a pre-yarn-spreading device, the fiber bundles are pre-spread by the pre-yarn-spreading device through an ultrasonic fiber expanding method, the pre-spread fiber bundles pass through the position between a rubber roller and a metal roller, liquid on the surfaces of the fiber bundles is removed under the common squeezing action of the rubber roller and the metal roller, afterwards, the fiber bundles enter a detection mechanism, through the detection mechanism, the speed of the fiber bundles is adjusted, the constant tension of the fiber bundles is guaranteed, the pre-spread fiber bundles with the tension and the speed well adjusted enter a main yarn spreading device, the fiber bundles are spread by the main yarn spreading device through the ultrasonic fiber expanding method, and the spread fiber bundles are rolled up through a traction crimping device. By means of the low-cost high-performance large-tow carbon fiber spreading device, the large-tow carbon fibers can be fully and effectively spread.