Water abundance evaluation of drenching tunnel is the premise for mine support design. In order to evaluate roof water abundance under the condition of alkaline water drenching tunnel, six indexes, including roof loose circle, crack growth degree, temperature, humidity, pH value and water drenching time, were selected as main indexes to evaluate the water abundance of roof. AHP (Analytic Hierarchy Process) focuses on the subjective evaluation of experts and the entropy weight method focuses on objectivity of data. Synthesizing the characteristics of the above two methods, this paper proposes a weight calculation method of water abundance index by coupling the improved AHP and entropy weight method through the least square method. Based on the field geological data of 50 groups in 5305 transport channelling in Zhaolou Coal mine, the water abundance evaluation of the drenching roadway roof was carried out based on the improved AHP method and entropy weight method. And the support design for the high water abundance zone is carried out based on the evaluation results. The results show that: The support design for water drenching roof can effectively control the development of loose circle and the water drenching condition of the roof, which has a reference significance for the whole mine and the eastern coal mine with similar geological conditions.