Under laboratory scale, with the cyclo-bio fluidized sand biofilter (CB-FSB) as the research object, the changes of the removal performance of ammonia-nitrogen and the nitrite-nitrogen, and the amount of amoA gene during the start-up period of cyclo-bio fluidized sand biofilter (CB-FSB) under different initial ammonia-nitrogen concentrations, water temperatures and filter expansion rates were studied in this paper. The experimental results showed that the time required for the start-up of cyclo-bio fluidized sand biofilter (CB-FSB) was shortened with the increasing of water temperature. The time required for the start-up of CB-FSB were 27, 25, and 23 days at 15℃, 20℃ and 25 ℃, respectively. The time required for the start-up of CB-FSB was shortened with the increasing of the initial ammonia nitrogen concentration. The time required for the start-up of CB-FSB were 24, 22, 21 days at 1 mg/L, 2 mg/L and 4 mg/L, respectively. There was no significant difference between 100% and 150% filter expansion rates for the start-up of CB-FSB, which was 21 days and 20 days, respectively. They were better than that with 50% expansion rate. The time required for the start-up of CB-FSB with 50% expansion rate was 27 days. The amount of amoA gene was related to the change of nitrite-nitrogen removal rate and increased with the increasing of initial ammonia-nitrogen concentration. The amount of amoA gene reached the peak at 4mg/L of ammonia-nitrogen concentration, which was 2.76 × 107 copies/g.