Abstract: Weinan is a major watermelon cultivation area in Shaanxi. However, continuous cropping and mismanaged field practices have led to local soil deterioration, which causes intensified diseases and pests attack and considerable watermelon quality decrease. To overcome this problem, a disinfectant is applied to local main cultivar, mini watermelon genotype‘Linglongwang’, to explore the effect on greenhouse watermelon growth, incidence of root-knot nematode, microorganism and soil enzymes. The results showed that the plant height and stem diameter increased with the increase of disinfectant concentration in the later growth stage of plant. Total fresh weight, yield and soluble solids all reached the highest under the disinfectant concentration of 52.5 kg/hm2. The yield per hectare also increased by 7.30% compared with that of CK. Moreover, the incidence of root-knot nematode decreased significantly with the increase of disinfectant level, the correlation coefficient was 0.7475. Soil total bacterial count decreased in the 0-10 and 10-20 cm soil layers after the addition of disinfectant, while the activities of four soil enzymes increased compared with that of CK. The activities of sucrase and alkaline phosphatase were also the highest at 52.5 kg/hm2 level of disinfectant application.