Filling carriers to anaerobic ammonium oxidation (ANAMMOX) reactor can improve Anammox biomass retention. But there are few researches about the influence of different characteristics of carriers on ANAMMOX biofilm growth. Two different suspending plastic carriers and two different sponge carriers were filled in the reactor to form ANAMMOX biofilm. The results showed that the NH4+ and NO2--N average removal rates of one sponge carrier were higher than one suspending plastic carrier on the whole. The EPS contents of sludge on sponge carriers and the speed of sponge carriers forming biofilm were higher than suspending plastic carriers. After biofilm forming for 30 days

the NH4+ and NO2--N removal rates of one sponge carrier with low density could be tested and the value of Δ(NO2--N)/(NH4+-N) was close to 1.32. After biofilm forming for 105 days

the NH4+ and NO2--N average removal rates of one sponge carrier with low density were 0.123 mg·L-1·h-1 and 0.160 mg·L-1·h-1

respectively. The value of Δ(NO2--N)/(NH4+-N) was 1.30

which was close to 1.32. The ANAMMOX activity of sludge on the sponge carrier with low density was the best. The abundance of anammox bacteria in the sludge on the sponge carrier with low density was the highest among the four types of carriers

which was 1.73×1010 copies·(g dry sludge)-1. The sponge carrier with low density had the best biofilm formation performance on the whole.