Changes of croplands often reflect the combined impacts of both natural environment changes and social agriculture activities. Such reflections manifested more significantly in agro-pastoral transition zones, e.g. in the North and West of China. In this study, cropland changes at the Yellow River–Huangshui River Valley, as a typical agro-pastoral transition zone in northwestern China, is analyzed in terms of the changes of the total amount and spatial pattern over the past 300 years (majorly in the Qing Dynasty). The reconstructed cropland data indicated a fluctuation of cropland areas in accordance with changes of regional climate conditions, natural hazards, agriculture activities and socio-economic development. A significant decrease of cropland in the middle of the 19th century was detected, which appeared a good consistency with the frequent natural disasters in the same period and the climate cooling trend across the whole 19th century. Though in the worsening conditions, three major copping strategies maintained and developed the local socio-agriculture system: (a) land reclamation policy encouraged immigrants and military farming; (b) construction of water conservancy facilities increased agricultural productivity; (c) increasing local Tibetans learned and transformed to implementing both agriculture and pastoral productions with flexibilities depending on climate conditions. The study demonstrates that the social-agriculture system held certain resilience, which can be maintained and enhanced with appropriate political, engineering, economic, and social-cultural measures.