The recirculating aquaculture system has the inevitable feature of discharging high-nutrient aquaculture solid waste and high-concentration nitrate wastewater. To solve this problem, a set of improved configuration of constructed wetlands treatment device were built in this study. In order to strengthen their N removal on the wastewater from recirculating aquaculture system, the improved constructed wetlands used aquaculture solid waste as additional carbon source and investigated the microbial community composition of the constructed wetlands by high-throughput sequencing. The results showed that with the increased addition of the amount of aquaculture solid waste, the N load in the influent of the constructed wetlands improved. When TCOD/TN in the influent was 8.78±0.41 and the depths of the anaerobic hydrolysis zone (A) were 30 cm and 50 cm, the improved constructed wetlands system had better TN, \rmNO_3^-\text -N
removal performance. At the phylum level, Proteobacteria was dominated in all constructed wetlands, with the relative abundance of 44.44%—62.87% in zone A and 61.93%—78.64% in constructed wetland packing zone B, respectively. Moreover, the improved constructed wetlands had a high relative abundance of denitrifying bacteria, which were mainly Silanimonas
(1.66%—23.42%) and Rivibacter
(4.74%—12.75%), while the relative abundance of denitrifying bacteria in the wetland packing zone B was higher than that in the lower anaerobic zone A. In addition, an uncultured Anammox bacteria genus (uncultured_c_Anammox_3
, 0.22%—0.33%) was also detected in the zone A. These results indicated that when the improved constructed wetlands was fed with aquaculture solid waste as the carbon source, nitrogen removal was mainly through denitrification process and a weak anammox effect was also involved. Thus, this study provided a preliminary theoretical guidance for the engineering practice of constructed wetland to deal with waste from recirculating aquaculture systems.