A method for controlling a gain of a multi-stage equalizer of a serial data receiver, applied to the serial data receiver, the serial data receiver comprising the multi-stage equalizer, wherein the method comprises the step of: Step S1, enabling the serial data receiver to receive a set of serial data; and is characterized by the steps of: Step S2, selecting a continuous first data sequence from the set of serial data according to a preset first rule; Step S3, selecting one or more continuous second data sequences from the first data sequence according to a preset second rule; Step S4, extracting a predetermined bit from each of the second data sequences; Step S5, calculating an equalization gain identifier of the data sequence by using each predetermined bit; and Step S6, controlling the gain value of the multi-stage equalizer according to the equalization gain identifier; the preset first rule in Step S2 comprises: Step A1, passing through a sliding window having a length of m+1, the sliding window sliding backward from a start bit of the set of serial data by a preset step; and Step A2, extracting the serial data corresponding to the sliding window to act as the first data sequence; the preset second rule in Step S3 comprises: Step B1, setting a plurality of sequence length values; Step B2, selecting a sequence length value from the plurality of sequence length values according to a preset third rule; and Step B3, selecting one or more continuous second data sequences from the first data sequence according to the sequence length value; wherein the preset third rule further comprises the steps of: Step C1, arranging each of the plurality of sequence length values according to the sequence length; Step C2, sequentially selecting one of the sequence length values, and each selected sequence length value is not repeated; or randomly selecting one of the sequence length values, and each selected sequence length value is not repeated. Step S1, enabling the serial data receiver to receive a set of serial data; and is characterized by the steps of: Step S2, selecting a continuous first data sequence from the set of serial data according to a preset first rule; Step S3, selecting one or more continuous second data sequences from the first data sequence according to a preset second rule; Step S4, extracting a predetermined bit from each of the second data sequences; Step S5, calculating an equalization gain identifier of the data sequence by using each predetermined bit; and Step S6, controlling the gain value of the multi-stage equalizer according to the equalization gain identifier; Step S2, selecting a continuous first data sequence from the set of serial data according to a preset first rule; Step S3, selecting one or more continuous second data sequences from the first data sequence according to a preset second rule; Step S4, extracting a predetermined bit from each of the second data sequences; Step S5, calculating an equalization gain identifier of the data sequence by using each predetermined bit; and Step S6, controlling the gain value of the multi-stage equalizer according to the equalization gain identifier; the preset first rule in Step S2 comprises: Step A1, passing through a sliding window having a length of m+1, the sliding window sliding backward from a start bit of the set of serial data by a preset step; and Step A2, extracting the serial data corresponding to the sliding window to act as the first data sequence; Step A1, passing through a sliding window having a length of m+1, the sliding window sliding backward from a start bit of the set of serial data by a preset step; and Step A2, extracting the serial data corresponding to the sliding window to act as the first data sequence; the preset second rule in Step S3 comprises: Step B1, setting a plurality of sequence length values; Step B2, selecting a sequence length value from the plurality of sequence length values according to a preset third rule; and Step B3, selecting one or more continuous second data sequences from the first data sequence according to the sequence length value; Step B1, setting a plurality of sequence length values; Step B2, selecting a sequence length value from the plurality of sequence length values according to a preset third rule; and Step B3, selecting one or more continuous second data sequences from the first data sequence according to the sequence length value; wherein the preset third rule further comprises the steps of: Step C1, arranging each of the plurality of sequence length values according to the sequence length; Step C2, sequentially selecting one of the sequence length values, and each selected sequence length value is not repeated; or randomly selecting one of the sequence length values, and each selected sequence length value is not repeated. Step C1, arranging each of the plurality of sequence length values according to the sequence length; Step C2, sequentially selecting one of the sequence length values, and each selected sequence length value is not repeated; or randomly selecting one of the sequence length values, and each selected sequence length value is not repeated.