The invention discloses an equalizer adjustment method, an adaptive equalizer and a memory storage device. The method comprises the steps of performing a handshaking operation by the memory storage device so as to establish a connection line with a host system; in the handshaking operation, receiving a first signal from the host system, and performing first modulation on the first signal by the adaptive equalizer; and after ending the handshaking operation, receiving a second signal from the host system, and performing second modulation on the second signal by the adaptive equalizer according to a modulation result of the first modulation so as to compensate the second signal; and adjusting the adaptive equalizer according to the modulation result of the second modulation. Therefore, the adjustment efficiency of the equalizer can be improved.