To explore the factors affecting the rapid start-up of chemical catalytic oxidation filter, three identical pilot-scale filters were employed to optimize the start-up process for simultaneous removal of iron (Fe), manganese (Mn), and ammonia from groundwater at various influent conditions. The results showed that chemical oxidation method could accelerate the start-up of filter. After 28days' operation, the simultaneous removal of iron, manganese, and ammonia could be achieved. A good dose iron was beneficial to shorten the start-up period of the filter. Various influent ammonia concentrations seemed to have no effect on the start-up of the filter. When the influent ammonia, Fe, Mn concentration was 1.5mg/L, 2.0mg/L and 1mg/L, respectively and the flow rate was 4m/h, it had demonstrated to be a feasible and quick start-up method. The maximum influent concentration of ammonia and manganese could reach up to 2.1mg/L and 2.7mg/L, respectively, which could meet the requirement for treating the polluted groundwater.