In order to effectively improve the collection rate of electric energy information in the low-voltage electricity collecting area under the requirement of Q / GDW 1379.4-2013 communication unit testing technical specification, a high-speed real-time and bidirectional intelligence electricity consumption information collecting system with an algorithm based on molecular band for power line carrier rate maximization is proposed. The algorithm combines the adaptive subcarrier modulation scheme of the Homeplug AV protocol, in which 2 ~ 30MHz is the carrier frequency, then the carriers are divided into some logical subgroups which contain some adjacent subcarriers. In the subcarrier allocation process, the median SNR algorithm, which is injected into the greedy distribution mechanism, is used. In this way, the subcarriers are allocated reasonably and the carrier rate is maximized. The simulation results show that the proposed algorithm has higher carrier rate than the traditional SNR threshold algorithm and Homeplug AV adaptive bit allocation algorithm. Compared with the traditional greedy algorithm, the carrier rate achieved is slightly lower which reduces computational complexity and hardware overhead.