Abstract: On the basis of 136 stations with annual precipitation amount, rainy days, precipitation intensity, the maximum daily precipitation amount records, and city and economic developmental data during 1961-2012 over northwestern China, the paper mainly studied the precipitation changing trends characteristics and artificial impact on them. The results showed that the precipitation of northwestern China has risen after 1980 in the mass; however the precipitation changing trends of eastern and western parts were opposite to each other and the central-western part has an upward trend, but downward trend for the eastern. In contrast to 1961-1978, the downward trend during 1979-2012 in the eastern part of northwestern China was noticeably declining, which formed a practice that the east developed region had an effect on increasing precipitation. Moreover, the changing trends during 1979-2012 for annual precipitation amount, rainy days, precipitation intensity, the maximum daily precipitation amount in other cities, petrochemical areas, and their downwind areas have increased markedly during 1961-1978. The contributions of urbanization, economic and petrochemical development to precipitation indexes are 10%-60% generally, and the petrochemical development has the most significant effect among them on raising precipitation. The multiple stepwise regressions indicated that social investment, industrial output value and services output value were the important economic indexes to significantly improved precipitation.