The embodiments of the present invention disclose a spectrum optimization method and device and digital subscriber line system, the method comprising: calculating according to acquired information of each of respective subcarriers on the DSL line to be optimized to obtain optimized transmission power of a subcarrier to be optimized in a DSL line to be optimized; calculating a transmission rate of the DSL line to be optimized according to the optimized transmission power; and comparing the transmission rate with a target rate of the DSL line to be optimized, and if the transmission rate is less than the target rate, updating the information of an optimized subcarrier, and performing a recalculation. The embodiments of the present invention can overcome the problem of the conventional art that it is difficult to converge the rate weighted coefficient, and improve the rate of a given subscriber line while reduce power loss caused by the given subscriber line to other subscriber lines in the same bundle of cables.