To further expand the application of anammox biotechnology, a novel zero-valent iron-assembled upflow anaerobic sludge bed reactor was employed to strengthen anammox performance under low temperature and shock load. Packed with sponge iron and polyester sponge, this novel reactor could speed up the recovery of anammox activity in 12 days and improve the adaptability of anammox bacteria at the temperature of 10-15 degrees C. The high nitrogen loading rate of 1109.2 mg N/L/day could be adapted in 27 days and the new nitrogen pathway under the effect of sponge iron was clarified by batch experiment. Moreover, the real-time quantitative PCR analysis and Illumina MiSeq sequencing verified the dominant status of Candidatus Kuenenia stuttgartiensis and planctomycete KSU-1, as well as demonstrated the positive role of sponge iron on anammox microorganisms' proliferation. The findings might be beneficial to popularize anammox-related processes in municipal and industrial wastewater engineering.