Abstract: For the optimal resources allocation of broadband power line communication OFDM system, the network structure of low-voltage broadband power line communication system is analyzed in this paper, based on which the resources allocation model of multiple sub-carriers for multi-users and multi-services is built under such cases as lack resources and many application constraints, and a cross-layer resource allocation algorithm based on fairness factor and user emergency is proposed to maximize system throughput by both meeting the minimum rate demand of RT business and ensuring fairness among NRT users. The simulation is implemented in a typical power line channel environment, and results show that proposed algorithm has better performance with the target of satisfying resource allocation model.