The effect of long-term or short-term exposure method on the nitrification in the fluvo-aquic soils incubated at 60% water-holding capacity and 28?C was firstly studied using acetylene as nitrification inhibitor. The results showed that nitrification in the fluvo-aquic soils were completely or nearly completely inhibited during the long-term exposure (14 d) to 10 ml/L or 100 ml/L acetylene. However, after short-term (12 h) exposure, partial inhibition of nitrification by acetylene was observed. The nitrification reoccurred on 3 d after the acetylene was removed and the nitrification ratio still reached high up to 99% at the end of the incubation, the results indicated that the net mineralization in the treatments of adding acetylene were negative value. The net mineralization in the treatment of the long-term exposure was lower than that of in the treatment of short-term exposure. Therefore, for ensuring the experiment design reasonable, it should be noticed that the recovery rate of nitrification and the changes in the mineralization in the sampled soil treated with acetylene inhibitor. For long incubation, it is a better method that long-term exposure to acetylene with periodically adding fresh air to soil, strictly controlling the aerobic time before the recovery of nitrification.