Method and apparatus for optimizing a decision threshold of an optical receiver is used to solve a problem of affecting system stability and reliability. The method comprises: determining a maximum value and a minimum value of an adjustment range of the decision threshold, and determining an adjustment step of the decision threshold (10); adjusting a decision threshold value within the adjustment range of the decision threshold, and separately detecting pre-FEC BERs corresponding to different decision threshold values (11); and searching for a minimum value in the detected pre-FEC BERs, a decision threshold value corresponding to the minimum value being an optimal decision threshold value (12). The apparatus comprises a decision threshold adjusting unit, a pre-FEC BER detecting unit, a decision threshold control unit and an optimal decision threshold determining unit.