The GIMMS and SPOT, which are the Normalized Difference Vegetation Index (NDVI), are utilized to analyze the historical evolution of the vegetation cover in Hilly and Gully Region of Northern Yan′an from 1982 to 2007 and relationship with climate factors. The results show that (1) The vegetation cover status is getting better continuously, although there were undulations in vegetation cover over past 26a in this region, and the averaged annual NDVI increased by 14.2%. The NDVI in summer is of maximum value and remarkable undulation, the NDVI value in autumn is next, while NDVI in spring and autumn has distinguished uptrend. NDVI values in each season are related with annual NDVI, and correlations of spring and autumn NDVI with annual NDVI are significant. The annual variation of NDVI is single peak type, while the spring NDVI increased slowly, the autumn NDVI decreased more rapidly. (2) There was no obvious correlation between annual average NDVI and annual temperature, and also poor correlation of NDVI in summer, autumn and winter with temperature in the same phase, only the NDVI in spring was correlated significantly with spring temperature. The impacts of temperature in March and April on vegetation are positive, the higher the temperature is, the faster the growth after returning-green stage of vegetation is. The temperature in June and July has negative lag influence on vegetation growth. The precipitation is one of the key factors influencing variation of NDVI, annual precipitation is related with NDVI values in July and September, which determines good or bad vegetation. The effect of monthly precipitation on the NDVI has hysteresis characteristic, the precipitation in preceding September affects the NDVI in April to June in next year, the monthly and previous precipitation affect the NDVI in June and July. (3) The vegetation cover has increased rapidly in Hilly Gully Region of Northern Yan′an since 1999, which maybe associated with increasing precipitation, and also with some non-climate factors by adaptive strategies in ecological conservation and environment protection, such as afforestation, mountain enclosure and fenced grassland.