Abstract: Study of dynamic process of soil N₂O transmitting, consuming and emitting under clear plastic film mulching needs to investigate the effects of mulching on soil N₂O discharge flux. Soil N₂O discharge fluxes by using static funnel and uncovering film-closed chamber methods and some soil properties were measured over two successive growing seasons of winter wheat, from March 2001 to June 2001 and from October 2001 to June 2002. Results showed that soil N₂O discharge fluxes measured at earth surface and at the depth of 10cm, 20cm soil layer significantly increased due to mulching compared with control. Changes of soil moisture in 0～5 cm layer and concentrations of soil nitrate in 10～20 cm layer in the fallow and the wheat fields were the reasons of the variance of soil N₂O discharge fluxes measured at earth surface by 85.23% and 92.11%, respectively, and thus they can be regarded as the main causes of the increase of soil N₂O discharge fluxes under clear plastic film mulching. These conclusions benefit to the scientific application of water and fertilizers in farmland under clear plastic film mulching and the spreading of this practice in western China for the sake of controling and reducing soil N₂O.