Abstract: To clarify the rule of cucumber green mottle mosaic virus disease in greenhouse grafted watermelon, the cause, spread and effect factors of the disease were studied. In greenhouse built by bamboos, healthy grafted watermelon plants were transplanted in virus-free soil conventionally or in low-density form. Top leaves of the plants were cut or leaves were cut by half after 6 days and 30 days. Then the wounds were dipped in virus to induce inoculation. Conventional transplanted plants grew naturally, while those in low-density form maintained independent. Healthy plants were induced by pruning with virus-contaminated scissors or fingers, and friction between healthy and sick vines induced plants as well. Then, natural spread of sick field and sick plants was investigated, and disease control effects of seeds without sick plants and interplanting melon plants were investigated too. Sick plants with symptoms were researched by visual method regularly, and confirmed by Double Antibody Sandwich Enzyme-linked immunosorbant assay (DAS-ELISA) method. Plants’ infection rate was high after inoculation. For transplanted plants in low-density form, inoculated plants which were transplanted after 6 days showed symptoms in 24 days, increased rapidly in 34 days and reached peak in 85 days, which were 4 days, 4 days and 30 days longer than those of plants inoculated 30 days after transplanting. Plants without inoculation showed symptoms in 70 days and reached peak in 95 days after transplanting. Conventional transplanted plants with inoculation shared a similar trend. Sick rates of plants with symptoms and plants with virus were closely related to the daily average temperature. Leaves between different vines and those on the same vines of sick plants displayed both obvious symptoms and hidden symptoms, and even lifetime hidden symptoms with virus. Sick rate of plants caused by friction between healthy and sick vines reached 100%, while methods of pruning with virus-contaminated fingers and scissors led to the rate of 91.7% and 83.3%. In sick field, virus spread adjacently, and then substantially. After getting rid of sick plants in the field, sick rates of melon plants and interplanting grafted plants were 82.4% and 77.0%, while the rates of disease control effect were 17.6% and 23.0% respectively. In conclusion, it takes 20 days’ incubation for greenhouse grafted watermelon (plants) to display sick symptoms from infecting cucumber green mottle mosaic virus. Afterwards, the amount of sick plants increases rapidly and reaches the peak. It has features of high temperature, short incubation, sudden increase and reaching the peak rapidly. The symptoms of hidden sick plants show in leaves between plants and vines, and also different leaves on the same vines. The influence of density of transplanting on the disease is not obvious. The disease spreads in the field adjacently first, and then substantially. The effect of friction between healthy and sick vines on virus transmission is great besides other methods. Succession cropping in sick field of the year has high probability of recurrence.