The present invention provides a dynamic power spectrum management method, a spectrum optimization system, and a client device, which can improve spectrum management. The method includes: calculating, from a tax factor containing user crosstalk information, a water-filling parameter corresponding to the case that total power of each user is below or equal to a threshold of total power of the user; calculating, from the water-filling parameter, power allocated to each user in each sub-carrier until convergence is attained for all users. Correspondingly, the present invention further provides a spectrum optimization system and a client device. In effect, the present invention can improve the spectrum management.