The spatial distribution and dynamic changes of vegetation in Northwest China were analyzed using SPOT/NDVI data during the period from 1998 to 2012. According to different regional NDVI, we analyzed the correlation between NDVI and climate factors such as temperature and precipitation. The results showed that: (1) vegetation coverage was low, the extremely low vegetation area was great in northwest China, and the extremely low vegetation area was mainly located in the southeast of Xinjiang and western Inner Mongolia; (2) degraded areas accounted for small proportion of total area of northwest China, and was mainly located in the Altai mountains, south of the Tianshan mountains and the north of Tarim Basin in Xinjiang. However,some areas had higher vegetation coverage that was improved slightly as a whole during the past years, the improved area was mainly located in surrounding of Tianshan mountains, edge of Junggar Basin and eastern Gansu; (3) on the annual scale, vegetation coverage in each area in northwest slowly increased in the recent 15 years, vegetation coverage in Xinjiang and Qinghai remained relatively stable, the vegetation coverage in Gansu, Ningxia and western region of Inner Mongolia presented the fluctuating trend, on the monthly scale, there were significant correlations between NDVI and both temperature and precipitation; (4) by comparison, the vegetation NDVI with temperature and precipitation had significant monthly correlations but less significant annual correlations in different areas. The responses of vegetation NDVI showed no significant time lag to temperature and precipitation in Xinjiang, Ningxia and Gansu, the response of NDVI exhibited noticeable lag to temperature, and NDVI to temperature and precipitation lag in Qinghai Province was not obvious. The NDVI of western region of Inner Mongolia had the lag to temperature, but it had no lag to precipitation.