This study, based on environmental archaeological studies focused on Qin'an County and Li County in Gansu Province, China, shows that during 8-7.3 ka BP few cultivated crop seeds were found. After 6.4 ka BP, during the Banpo period, many crop seeds appeared, indicating the development of agriculture. Millet agriculture in this area appeared and flourished a little later than in the Central Plain of China. Climate change is an important factor that influenced the development of agriculture in this area. The rapid expansion of agriculture during late Yangshao and Changshan benefited from the humid and warm climate in the mid-Holocene, especially the emergence of rice. After 4 ka BP, climate became drier, and agriculture began to decline. So Siwa Culture is characterized by pastoral economy, until the Eastern Zhou period, agriculture began to recover, when wheat and barley appeared in Li County, indicating diversification of agriculture of this time.