Abstract: Since 1980s the food condition and inhabitation environment of cotton bollworm have been changed by the changing of cultivation system of crops.The main reason for the outbreak of cotton bollworm in the Yellow River Basin was the the destroy of ecological balance.Natural enemy,the same as water,soil,light,air,and heat,is part of agro-natural resources.Then is was suggested that the conservation and encouragement of natural enemies be included in the major projects of ecoagricultural developing strategies.The studies of key control techniques and basic theory should be strengthened up.