Abstract: The authors proposed a quasidynamic chamber method for measurement of NH3 emission from a soilplant system. This method showed that the recovery rate is 89.0％± 4.9% for measurement of NH3 volatilization, which is in agreement with the recovery rate of a windtunnel method. It can also yield results consistent with those measured by a limitedly ventilated close chamber method. There is a significant exponential correlation between diurnal NH3 emissions and temperature (r<0.05). The optimum time for an intermittent measurement using the quasidynamic chamber method was proposed at around 0900LST or 1600LST. The NH3emission caused by an N fertilization event could be best captured after 1－2 weeks using the quasidynamic chamber method. Using the quasidynamic chamber method, the NH3N losses from the applied urea into a wheat field in Shanxi Province during the wheat jointing stage were observed at 3％－5%.