A controller for data strobe signal (DQS) position adjustment includes, when the controller obtains margin effective widths of all data signals in a transmission bus, it determines a left boundary and a right boundary based on the margin effective widths, where the left boundary is a largest value in minimum values of the margin effective widths of all the DQs, and the right boundary is a smallest value in maximum values of the corresponding margin effective widths when all the DQs are aligned with the left boundary. The controller calculates a first central position based on the left boundary and the right boundary, where the first central position is a center of a smallest margin effective width obtained after all the DQs are aligned during read data training, and adjusts a delay line (DL) of the DQS to the first central position.