This study was carried out to control the onion white-rot disease by using compost alone or in combination with some other treatments such as Humic acid, sulfer, Trichoderma viride and gool herbicide. Six isolates of Seclerotium cepivorum (the causal fungus of the onion white – rot disease) were tested in this experiments. Isolate No. 1 was the most aggressive as it incited white – rot disease on three onion cultivars (Giza 20, Giza 6 and Italy).  The soil application with compost which added at planting gave the lowest mean disease incidence under greenhouse conditions. However compost application alone or in combination with other amendments on infection with Sclerotiomum cepivorum (isolate Sc₁) on onion (cvs. Giza 20 and Giza 6) significant decreased in the disease incidence(percentage of infection) as compared with the infected untreated control. Treatments of compost with gool was the most effective treatment and reduced percentage of infection with white rot on Cv. Giza 20 and Cv. Giza 6, to 3.9% and 6.95% compared to 44.6% and 53.75% for the untreated control for both Cvs. respectively, with 89.1% mean disease reduction under field conditions.   Investigating of the chemical characteristics associated with onion tolerance to S. cepivorum reveald  that he total phenolic content in most tolerant non-inoculated cv. Italy was obviously higher than that the most susceptible cv. Giza 20. being 9.8 mg/g. f.w. and 10.9 mg/g.f.w, respectively. Also, planting of onion plants in soil infested with S.cepivorum isolates significantly increased mean total phenolic content in bulbs reach 17.32 mg/g. f.w. in the most  resistant cv. Italy of onion compared to the susceptible cv. Giza 20 reached to 13.8 mg/g.f.w.. Also, the application of compost alone or in combination with other substances significantly increased shoot length, number of leaves / plant and yield.