Based on the land use maps in 1995

2000 and 2010

as well as the statistical data of cropland use in Zhengning County of Gansu Province

cropland distribution change and cropland protecting pressure were studied before and after the "grain for green" project by using ENVI

ArcGIS and SPSS.After the "grain for green" project

most of low-quality slope croplands were returned to forestland

and some of high-quality plain croplands were occupied by expanding construction land.The spatial pattern of croplands changed from scattered and irregular to concentrated and regular distribution.Factors for cropland protecting pressure in Zhengning County can be divided into artificial

policy and natural factor.The artificial factor is mainly de-termined by people's living standards and crop production conditions

the policy factor is affected by restora-tion subsidy

and the natural factor is reflected by damage area of cropland.In order to relieve cropland pro-tecting pressure in the area where the "grain for green" project was implemented

more emphasis should be placed on protecting the existing plain cropland from being occupied by construction land

stabilizing a con-siderable ecological compensation level for avoiding reclamation of the returned cropland

and limiting agro-chemical inputs in order to reduce the risk of agricultural non-point source pollution?