A field experiment was conducted to study the spatiotemporal variation of soil moisture in an oasis cotton field with different tillage modes.Results showed that in 0-120cm soil layer,the maximum soil moisture content was observed for no-tillage with mulching stalk;the medium,for no-tillage with standing stubble;and the minimum,for conventional tillage and tillage with film mulching.Soil moisture contents for no-tillage with mulching stalk and no-tillage with standing stubble were higher than those for conventional tillage and tillage with film mulching in 0-20cm soil layer,being significantly different in 0-5cm soil layer and no difference in 20-120cm soil layer.There was an obvious gradient of soil moisture content in the depths for the three tillage modes.Soil moisture contents for the three tillage modes decreased significantly with time before irrigation.The difference between no-tillage and tillage was greater at the early stage than the later stage.High soil moisture content was observed in tilled field after irrigation.Soil moisture in top soil layer was steady for no-tillage with mulching stalk and tillage with film mulching and remarkably varied for no conventional tillage and no-tillage with standing stubble.