Abstract: In order to clarify mechanism of wheat yield increase in northwest China，on basis of consulting relevant research results，effects of straw mulching on wheat yield and its components were analyzed.It was found that no-tillage straw mulching could increase wheat yield by 10%～20% in northwest regions compared with no mulching，and effect of yield increase was remarkable.Reasons for increase in yield were analyzed，and it was found that mechanism of wheat yield increase lied in effective regulation of farmland ecological effects that straw mulching could significantly increase number of large soil aggregates and improve stability of soil structure，increase soil water content of 0～200 cm soil layer，adjust ground temperature to avoid severe temperature fluctuations，increase soil microbial community and soil fertility，and improve soil enzyme activity.Effects of straw mulching on wheat yield and farmland effects were mainly summarized，aiming to provide a theoretical basis for wheat straw mulching in northwest China.