Abstract: Cucumber of "Zhongnong 26" and marigold were intercropped in substrate containing root-knot nematodes. The effects of intercropping density of marigold on the growth, physiological characters, yield of the cucumber and the control effect on Meloidogyne incognita were studied. Results showed that, when the intercropping density of marigold to cucumber is 1 to 1, the number of nematodes reduced by 49.3%, the chlorophyll content was significantly higher while the activities of SOD, POD and CAT decreased significantly in comparision with those of CK (not intercropped with marigold). However, the yield of cucumber was increased by 39.7% than that of CK. When the intercropping density of marigold to cucumber is 3 to 1, the number of nematodes reduced by 66.7% compared with that of CK. The fresh and dry weight of shoot was decreased. However, the chlorophyll content, antioxidant enzyme activity and yield of cucumber were same as those of CK. When the intercropping density of marigold to cucumber is 2 to 1, the number of nematodes reduced by 66.7% compared with that of CK and the disease index reduced by 51.4%. The chlorophyll content in leaves of cucumber was higher and the SOD, POD, CAT activities were lower compared with CK. As a result, the yield of cucumber increased by 35.7% and there was no significant difference compared with that of CK. These results indicated that 2 to 1 is the appropriate intercropping density of marigold to cucumber to control the damage caused by root-knot nematodes.