Abstract: The characteristics of soil solarization and efficiency against watermelon wilt (Fusarium oxysporum f.sp. niveum), with different colors, different layers of plastic mulching and irrigation were investigated inside greenhouses during 2004 and 2005 at hot season in Ningbo, China. The results showed that the irrigation and plastic mulching treatment could significantly add the soil temperature at 5, 10, 15 and 20 cm depths and increase 10~15℃ compared with the CK(un-mulched). It was also found that warming effect of bilayer transparent mulching was the best and monolayer transparent mulching was followed. After mulching 10 d by the monolayer transparent membrane, soil temperature at 5~20 cm depths could be maintained above 40℃ throughout the day. Watermelon wilt test showed that the control effect of the first crop of continuous cropping watermelon wilt covered by the monolayer transparent membrane more than 25 d was 100% and the anti-efficiency of the second crop covered by same membrane was also more than 84.5%. The laboratory test showed that the death time of Fusariurn oxysporurn f. sp. niveum in watermelon roots was 4 d in 41℃ and 1 d in 43℃. Therefore, it is very effective to control the presence of watermelon wilt by monolayer plastic mulching at hot season in Southern China.