Considering the broadband linear periodic time varying（ LPTV） channel

propose a bit-loading and power allocation algorithm adapt to broadband power line. The algorithm can be divided into two steps

the first step uses Lagrange multiplier method to allocate bit and power

the second step uses binary search method for rapid iteration. The simulation results show that compared with the traditional algorithm

this algorithm can guarantee transmission rate and also significantly reduce computational quantity. The algorithm can overcome the broadband power channel time-varying characteristics

improve the system performance

and can be used in actual power line communication.