Abstract: Effects of atmospheric CO2 concentration on soil nutrients and cotton plant dry weight were studied by field plot experiment. The results showed that under normal atmospheric CO2 concentration (CK), nitrogen fertilizer reduced the soil pH, under C540, C720 level, in no nitrogen treatment, the soil pH value decreased then increased, in nitrogen treatment,soil pH rose then downed. With the increase of atmospheric CO2 concentration, soil available nitrogen increased. Organic carbon showed different changes in different soil layers, 0~20 cm it showed a downward trend, in 20~40 cm it downed then rose. Cotton aboveground dry biomass increased with atmospheric CO2 concentration increasing. Under CK level nitrogen fertilizer made cotton root to shoot ratio decreased, while under C540 and C720 treatments, the results was inconsistent.