By batch experiment, the optimal working parameters of ultrasonic enhancement of Anammox bacteria activity were obtained:ultrasound frequency of 25kHz, ultrasound time of 3 min and ultrasound intensity of 0.2 W/cm²; afterwards a fixed-bed reactor was inoculated with the traditional activated sludge to start up Anammox process under the optimal ultrasound enhancing conditions. During the whole experiment, the temperature was maintained at 35℃. In the start-up stage, the hydraulic retention time (HRT) was 2 days and the influent NH₄⁺-N and NO₂^--N concentrations were both controlled at 70mg/L. After 38days operation of the reactor, the Anammox activity appeared for the first time. After 53days operation, NH₄⁺-N and NO₂^--N removal rates were up to 30.81mgN/(L·d) and 34.97mgN/(L·d) and their corresponding removal efficiencies reached 88.03% and 99.91% respectively, and the total nitrogen removal rate and removal efficiency reached 60.34mgN/(L·d) and 86.20% respectively. R₁and R₂ were stabilized at 1.14 and 0.18. In the nitrogen loading enhancement stage (day 53~135), when the influent NH₄⁺-N and NO₂^--N loading rates were both maintained at 380mg/(L·d), the average removal efficiencies of NH₄⁺-N and NO₂^--N were 82.74% and 97.89%. The max NH₄⁺-N and NO₂^--N removal rates were up to 320.67mgN/(L·d) and 379.85mgN/(L·d), while the max total nitrogen removal rate and efficiency were 698.00mgN/(L·d)and 91.84% respectively. At the end of the nitrogen loading enhancement stage, R₁ was stabilized at 1.18 while R₂ was close to 0. In the reactor, Anammox bacteria predominated and a small amount of denitrifying bacteria coexisted with them so as to improve the total nitrogen removal.