The invention discloses a scrambling method and device for a physical coding sublayer. The scrambling method comprises the steps of receiving scrambled data in the current round through a shift register to perform packet transmission of each packet data according to a physical medium, and moving a linear sequence stored in the shift register leftward by the length of one packet data within each period; scrambling the linear sequence stored in the shift register according to a standard scrambling polynomial; detecting the position of the current packet data in the scrambled data in the current round through a state machine, and directly outputting a scrambled result when the current packet data is the non-last packet data in the scrambled data in the current round; outputting the scrambled result after inserting a boundary tag if the current packet data is the last packet data in the scrambled data in the current round. The scrambling device comprises the shift register, a scrambler and a data output module. The scrambling method and device disclosed by the invention has the advantages of high scrambling efficiency and low scrambling delay.