A technology of dynamically adjusting an optical power receiving range of an optical module in a passive optical network is provided. In an optical module it includes an optical signal receive end receives an optical signal, an avalanche photodiode converts the optical signal into an optical current, an optical power detection module obtains an optical power value of the optical current, a main control chip adjusts a resistance value of a variable feedback resistor circuit according to the optical power value, and a transconductance amplifier outputs a voltage according to the resistance value of the variable feedback resistor circuit and the optical current. In this way, a bit error rate is effectively reduced, an optical power receiving range of the optical module is expanded, and system robustness is enhanced.