This thesis attempts an environmental analysis of the Colorado River in Southwest America.and examines the early issues of economic development and environmental protection on the Colorado River Basin from a historical perspective.The thesis first provides a brief description of the geography of the Colorado River,paying special attention to the early exploration of the Colorado River by Native Americans and later European colonizers as well as their different attitudes toward nature.Then the thesis looks at the forces of economic development and nature preservation in the progressive era against the arid setting of the Southwest.In the conclusion,the author demonstrates the importance and necessity of the environmental protection of the Colorado River in the beginning period of the America West.