A method for determining a main chain of a blockchain, a device, and a storage medium. The method comprises: determining, on the basis of a detection result that it is detected that a blockchain has at least two fork chains, weights of blocks in the fork chains (110); determining, on the basis of the weights of the blocks comprised in the fork chains, the weights of the fork chains (120); and determining a main chain from the fork chains on the basis of the weights of the fork chains, and rolling back the fork chains except for the main chain (130).