Abstract: With irrigation water amount controlled by E601 type evaporator, the authors studied the effects of different water supply conditions in different growth stages on water production function of mini-watermelon, and calculation directly path coefficient and indirectly path coefficient among plant height, stem diameter, leaf area index (LAI), shoot dry weight, root dry weight and yield by path analysis method. The experiments included four levers of water supply at different growing stages of mini-watermelon. The results indicated that the relationship between total yield and the total amount of water consumption was quadratic parabola, and the optimal irrigation amount was 107 mm. Water sensitivity index went down successively from fruit spreading growth stage, blossoming and bearing fruits stage, fruit maturing stage and seeding stage. The correlation coefficient between stem diameter and yield, LAI and root dry weight reached significant level and extremely significant level. The stem diameter and root dry weight can be used as evaluation indexes.