A method for adjusting a serial data signal having multiple sets of bits includes the following steps. First, one set of bits in the serial data signal is over-sampled to generate a first set of over-sampled bits. Next, every adjacent two bits of the first set of over-sampled bits are compared to generate one set of edge bits. Then, a delay operation is determined according to the set of edge bits. Afterwards, a displacement operation is executed on next sets of bits in the serial data signal according to the delay operation.