The invention discloses a method and device for decoding a stair code, and the method comprises the steps: 1, obtaining the length of a sliding window, and continuously obtaining L subcode blocks as to-be-decoded subcode blocks in the sliding window according to the receiving time sequence from the front to the back, wherein L is a positive integer; 2, grouping the to-be-decoded subcode blocks fordecoding, updating the to-be-decoded subcode blocks according to a decoding result, obtaining updated subcode blocks, and outputting the former M new subcode blocks as the decoding result, wherein Mis less than L; 3, sliding the sliding window backwards by the length of M subcode blocks, recombining the remaining updated subcode blocks in the sliding window and the subcode blocks sliding into the sliding window as the to-be-decoded subcode blocks in the sliding window, and returning to step 2 till the coding result of all subcode blocks is outputted. The method reduces the implementation complexity of a hardware circuit, and reduces the time delay of decoding.