Abstract: Efficiency of different concentrations of Trichoderma longibrachiatum T6 against Meloidogyne incognita and its rhizosphere colonization in cucumber were determined in greenhouse experiments. The results of rhizosphere colonization experiments showed that the number of colonies in cucumber soil and root increased significantly ten weeks after inoculation with the second stage juveniles of M. incognita and different concentrations of T. longibrachiatum T6, and there was significant difference in different concentrations of T. longibrachiatum T6, e.g., the maximum numbers of colonies in soil and root were 7.8×10⁷ and 6.3×10⁵ CFU·mL^-1 respectively after treated with the spore suspension of 1.5×10⁷ CFU·mL^-1. Greenhouse experiments results showed that different concentrations of T. longibrachiatum T6 had significant control effect on different life stages of M. incognita, and the control effect increased with the concentration of T. longibrachiatum T6. T. longibrachiatum T6 significantly increased plant height, root length, aboveground and root fresh mass of cucumber inoculated by M. incognita. T. longibrachiatum T6 could colonize in cucumber rhizosphere, had control effect on M. incognita, and significantly improved the growth of cucumber.