A way of thermal-humidity load distribution of direct-return chilled water system based on the suboptimal group was proposed. And the sub-optimization method of variable step size combined with the random walking was adopted. After obtaining suboptimal group of thermal-humidity load distribution in different load rate in the air-conditioning season, it would analyze random behavior and statistical law of the suboptimal group. So that the optimal control strategy and adaptability of chilled water system could be explored in constraint of complex variable. The results showed that the most overlapped ratio of the suboptimal solution of terminal numbers reached 24 percent under the four load rate, for example, 40%, 60%, 80%,100%. A correlation between random behavior of suboptimal group and strategy of heat and moisture load distribution for chilled water system was found, and the optimal solution of terminal numbers nearer cold sources had the higher overlapped ratio, better adaptability of distribution strategy, larger weight.