Great hazards could be easily caused by high concentrations of ammonia in chick houses, which are almost inclosed and heated up with low ventilation rate. A technology of in-situ unpowered biofiltration was studied to remove ammonia gas in chick houses. Analytical parameters included inorganic nitrogen compounds, pH value, and electrical conductivity (EC) of the superficial and inner media. Results of 37d operation in synchronization with a whole circle for chick brooding showed that, in the superficial media, the maximum ammonia elimination capacity was higher than 4.03g/kg, the maximum ammonium nitrogen absorption ability achieved 1.59g/kg, the highest nitrate nitrogen content achieved 2.69g/kg, and nitrite nitrogen content was nearly 0, pH value showed a decreasing trend in the range of 8.81～7.39, and EC kept increasing with the highest increment of 2.30mS/cm. However, the contents of ammonium, nitrate and total inorganic nitrogen as well as EC in inner media were far lower than those in superficial media. It suggested that further work should be done towards optimization of media depth setting. In conclusion, in-situ unpowered biofilter exhibited high ammonia elimination capacity and could be applied for contaminated air degradation in chick houses.