Abstract: For the purpose of quantitatively evaluating water resources carrying capacity in the Sanjiang plain and directing the regional agricultural production scale and socioeconomic development, the evaluation index system and criteria were established firstly. Then the projection pursuit evaluation model based on particle swarm optimization algorithm was used to comprehensively evaluate and classify water resources carrying capacity in the Sanjiang plain. Finally the regional differences of water resources carrying capacity of six cities and one town in the Sanjiang plain were analyzed by utilizing the visualization function of ArcGIS software. The results indicated that the water resources carrying capacity of the whole area of Sanjiang plain in 2008 belonged to grade III. Shuangyashan city, Qitaihe city and Muling city belonged to grade II which implied high carrying capacity and weak non-pressure state of water resources, and Jixi city, Hegang city, Jiamusi city and Yilan town belonged to grade III which implied moderate carrying capacity and compatible state between water resources exploitation and socioeconomic development. Along with the rapid growth of regional society and economy, a scientific and reasonable exploitation and development program of water resources could be made by using the results of the research to guarantee a continuable supply capacity of water resources for socioeconomic development.