A method for automatically adjusting a gain of a multi-stage equalizer of a serial data receiver, applied to the serial data receiver, wherein, the serial data receiver provides a gain circuit, the gain circuit comprises a multi-stage equalization circuit, and each stage of the equalization circuit is arranged in series; the automatic adjusting method is characterized by the steps of: Step S1, setting a corresponding serial number for each stage of the equalization circuit, the serial number being from 1 to n in sequence; Step S2, selecting a stage of the equalization circuit corresponding to the serial number from the gain circuit according to a preset rule in each round of selection; Step S3, adjusting the selected stage of the equalization circuit to obtain standard adjustment values of corresponding serial numbers; and Step S4, adjusting the equalization circuit which stages are greater than or equal to the corresponding serial number according to the standard adjustment values of corresponding serial numbers; wherein the preset rule in Step S2 comprises: Step C1, counting the number of the equalization circuits; Step C2, calculating the serial number of the selected equalization circuit using the following formula according to the number; { A = 1, m = 1 A = 2 m − 1 − 1 2 m − 1 × n, m ≥ 2 wherein A represents the serial number of the selected equalization circuit, and when A is not an integer, A is set to an integer closest to A and greater than A; m represents a current round of selection; and n represents the number of the equalization circuits. the serial data receiver provides a gain circuit, the gain circuit comprises a multi-stage equalization circuit, and each stage of the equalization circuit is arranged in series; the automatic adjusting method is characterized by the steps of: Step S1, setting a corresponding serial number for each stage of the equalization circuit, the serial number being from 1 to n in sequence; Step S2, selecting a stage of the equalization circuit corresponding to the serial number from the gain circuit according to a preset rule in each round of selection; Step S3, adjusting the selected stage of the equalization circuit to obtain standard adjustment values of corresponding serial numbers; and Step S4, adjusting the equalization circuit which stages are greater than or equal to the corresponding serial number according to the standard adjustment values of corresponding serial numbers; wherein the preset rule in Step S2 comprises: Step C1, counting the number of the equalization circuits; Step C2, calculating the serial number of the selected equalization circuit using the following formula according to the number; { A = 1, m = 1 A = 2 m − 1 − 1 2 m − 1 × n, m ≥ 2 wherein A represents the serial number of the selected equalization circuit, and when A is not an integer, A is set to an integer closest to A and greater than A; m represents a current round of selection; and n represents the number of the equalization circuits. Step S1, setting a corresponding serial number for each stage of the equalization circuit, the serial number being from 1 to n in sequence; Step S2, selecting a stage of the equalization circuit corresponding to the serial number from the gain circuit according to a preset rule in each round of selection; Step S3, adjusting the selected stage of the equalization circuit to obtain standard adjustment values of corresponding serial numbers; and Step S4, adjusting the equalization circuit which stages are greater than or equal to the corresponding serial number according to the standard adjustment values of corresponding serial numbers; wherein the preset rule in Step S2 comprises: Step C1, counting the number of the equalization circuits; Step C2, calculating the serial number of the selected equalization circuit using the following formula according to the number; { A = 1, m = 1 A = 2 m − 1 − 1 2 m − 1 × n, m ≥ 2 wherein A represents the serial number of the selected equalization circuit, and when A is not an integer, A is set to an integer closest to A and greater than A; m represents a current round of selection; and n represents the number of the equalization circuits. Step C1, counting the number of the equalization circuits; Step C2, calculating the serial number of the selected equalization circuit using the following formula according to the number; { A = 1, m = 1 A = 2 m − 1 − 1 2 m − 1 × n, m ≥ 2 wherein A represents the serial number of the selected equalization circuit, and when A is not an integer, A is set to an integer closest to A and greater than A; m represents a current round of selection; and n represents the number of the equalization circuits.