Abstract: In china, vegetable acreage was increasing year by year, and the problems of soil nutrient out of balance, soil acidification and salinization were becoming more and more prominent. Soilless substrate cultivation has unique advantages in relieving the increasingly tense land resources, preventing the rapid degradation of soil and ensuring the quality and safety of agricultural products. However, in order to reduce the cost of substrate, the technology of cyclic utilization of cultivation substrate is necessary. Common technologies include chemical disinfection, solar disinfection and steam disinfection, but there are some unsolved vulnerabilities of incomplete killing of pathogenic bacteria due to heat uneven transfer. In order to resolve this problem, a kind of disinfection machine was designed. This machine could disinfect continuous cultivation substrate by means of the jacket heating with heat transfer oil. The maximum volume of this machine was 5000 L, and it realized automatic feeding, automatic mixing, automatic controlling temperature and automatic discharging. In this paper, we studied the main obstacle factors for the utilization of watermelon continuous cultivation substrate, and carried out correlative operating parameter (e.g. total tray capacity, moisture content, disinfection method and time) optimization for this equipment and verify the result of cultivation with disinfected substrate in the field. At the same time, we calculated the economic cost and put forward the promotion suggestions. Results indicated that physical and chemical properties of substrate changed significantly after cultivation of watermelon, and the bulk density increased while the porosity decreased significantly (P<0.05). The total nitrogen content, available nitrogen and available potassium decreased by 33.0%, 40.3% and 33.5%, respectively. All the physical and chemical properties of substrate still met the reuse requirement for watermelon cultivation. The pathogenic bacteria population explosion (the population of Fusarium oxysporum changed from 0 to 5.3 ×103 cfu/g) was the main obstacle factor for reusing this substrate. Based on this machine, the optimum disinfection operating parameter of watermelon continuous cultivation substrate were as follows: Input quantity was 3 m³ and substrate water content was about 40%, disinfecting time was 2-2.5 hours at high temperature of 70 ℃. And based on the above parameters, the economic costs were controlled at 42.25-53.50 RMB/m3 with this equipment, which was below 6% of the cost of the new substrate. Field experimental results showed that no watermelon fusarium wilt broke out in disinfected substrate treatment, because the population of Fusarium oxysporum had no significant increase as compared to control. Meanwhile, there was no significant difference in watermelon growth parameters (e.g. plant height, stem diameter in middle stage of watermelon growth, plant dry weight, single fruit weight, and plot yield after harvest) between the new substrate and disinfected substrate. Therefore, this machine met the requirements of disinfection continuous cultivation substrate which could be applied well to actual agricultural production. Of course, considering the cost of this equipment, the best promotion mode should be through substrate marketing enterprises, who could conduct business plate of continuous cultivation substrate disinfection or trade in allowance.