The present invention provides a decoding method and device for Reed-Solomon (RS) codes. The method includes the following steps: A: filling data to be decoded in a byte interleaver by column in turn; B: performing cyclic shift to data in a check region of the byte interleaver by row and/or by column, so as to make the data of each row in the check region become check data in sequence of data of corresponding row in an information region of the byte interleaver; C: performing RS decoding by row method, and writing information data of each row obtained after decoding into the corresponding row in the information region of the byte interleaver in turn; and D: reading business data of the decoded information data from the information region of the byte interleaver by column. The method and device of the present invention can achieve the best interleaving effect.