The present invention provides a method and an apparatus for supplying power to a 300 PIN MSA 40Gb TRANSPONDER. The apparatus comprises a power control module (31), a second resistor (R 2 ), a third resistor (R 3 ) and a compensation circuit. The power control module (31) comprises an output terminal (311) and a reference voltage terminal (312). The output terminal (311) supplies power to the 300 PIN MSA 40Gb TRANSPONDER through an Adaptable Power Supply (APS) Digital pin (33) of the 300 PIN MSA 40Gb TRANSPONDER. The reference voltage terminal (312), one terminal of the second resistor (R 2 ), one terminal of the third resistor (R 3 ) and one terminal of the compensation circuit are connected with each other. The other terminal of the second resistor (R 2 ) is connected with an APS Set pin (35) of the 300 PIN MSA 40Gb TRANSPONDER. The other terminal of the third resistor (R 3 ) is connected with an APS Sense pin (34) of the 300 PIN MSA 40Gb TRANSPONDER. The other terminal of the compensation circuit is ground
