Cucumber Fusarium wilt is an important soil-borne disease that restricts cucumber production in all areas of the world. To explore the preventive effects of Cleome spinosa on cucumber Fusarium wilt, five different doses of Cleome spinosa powder including 0, 0.1, 0.2, 0.3, and 0.4 g/dish were applied to cucumber plant infected with Fusarium oxysporum f.sp. cucumarinumat Northeast Agricultural University. The data thus collected on various parameters were subjected to one-way analysis of variance (ANOVA) under Completely Randomized Design (CRD). The difference in treatment means were separated using Duncan’s Multiple Range (DMR) Test. A 100% inhibition rate on F. oxysporum mycelium was achieved when the dose of C. spinosa powder rose to 0.3 or 0.4 g/dish. As the concentration of the Cleome spinosa extract increased, the inhibitory effects on diameters and dry weight of mycelium also increased. Median inhibitory concentration of C. spinosa on mycelium was was 45.12 mg mL^-1.Gas chromatography-mass spectrometry identified twenty-one sorts of volatile constituents of Cleome spinosa, including heterocyclic compounds, alcohol, chromene, ester, acid and long chain alkanes. Twelve components of F. oxysporum were extracted by fumigation. Among those components, paeonol, linalool and theaspirane had antimicrobial activities against F. oxysporum, with inhibition rates of 73.9%, 75.9% and 80.4%, respectively. However, tetradecyl-oxirane, tetracosane, heptacosane, 3-ethyl-2-hydroxy-2-cyclopenten-1-one, octacosane, 1,1,4A-trimethyl-3,4,4A,5,6,7-hexahydro-1H-naphthalen-2-one,6,10,14-trimethyl-2-pentadecanone, methyl alpha-linolenate and pentatriacont-17-ene had no inhibitory effect against F. oxysporum. Those results suggested that the components of Cleome spinosa powder could effectively restrain cucumber Fusarium wilt.