Biological community including carabids and spiders were investigated in 30 various fields margins and 10 related fields by pitfall trap in Quzhou area of North China Plain.It was concluded that biodiversity index and numbers of biological groups in field margins are higher than those in the related crop fields.There is a given relationship between the attributes of field margins and biodiversity.The control of structure and vegetation in field margins would be the possible way to protect natural enemy such as carabides and spiders. Biological community including carabids and spiders were investigated in 30 various fields margins and 10 related fields by pitfall trap in Quzhou area of ​​North China Plain. It was concluded that biodiversity index and numbers of biological groups in field margins are higher than those in the related crop fields. there is a given relationship between the attributes of field margins and biodiversity. The control of structure and vegetation in field margins would be the possible way to protect natural enemies such as carabides and spiders.