Abstract: Control efficacies of chitosan oligosaccharides in combination with neodymium against Fusarium wilt in cucumber (cv. Jinyan 4) were investigated. Results indicated that control efficacies of 50 mg/L chitosan oligosaccharides in combination with 10 mg/L neodymium were 74.7%, 22.0% and 43.8% higher than those resulted from treatments with 50 mg/L chitosan oligosaccharides and 10 mg/L neodymium alone. The influence of chitosan oligosaccharides and neodymium in single and combinative treatment on activities of defense enzymes of cucumber seedlings were analyzed. Results demonstrated that chitosan oligosaccharides in combination with neodymium increased the activities of phenylalanine ammoialyase, peroxidase, polyphenol oxidase, β-1,3-glucanase of cucumber seedling roots.