The invention discloses an error code negotiation method of a quantum key distribution system, solves the problem that the negotiation efficiency is reduced due to collision in the error code negotiation process of a conventional Cascade algorithm, and belongs to the technical field of quantum communication. The method comprises the following steps: S1, in the first round, carrying out parallel processing on a binary lookup odd-even error correction process; S2, in the second round, obtaining blocks containing odd errors, placing the block with the highest collision probability in a processingset, and placing the rest blocks in an error set; S3, calculating the collision probability of blocks in the error set and the processing set, putting n blocks with the minimum collision probabilityin the error set a into the processing set, conducting one-step binary search odd-even error correction on the blocks in the processing set in parallel each time, when the error blocks are found, removing the blocks from the processing set, determining the positions of the error blocks in the previous round, and if the blocks are in the error set, removing the blocks are removed, and otherwise adding the blocks are added into the error set; S4, repeating S3 until the error set is 0, and turning to S5; and S5, carrying out all the following rounds according to the S2 to S4.