Abstract: The effects of different organic composts such as chicken manure, cow manure and corn stalk, respectively combined with the Purpureocillium lilacinum in suppressing tomato root-knot nematode were determined under pot culture conditions. The results showed that the combined use of the chicken manure, cow manure and corn stalk with P. lilacinum can significantly suppress gall numbers on tomato roots with the control efficacy of 78.3%,59.7% and 61.3%, higher than use of P. lilacinum alone. In addition, they can effectively increase the plants stem diameter, plants height and aboveground fresh weight. Among three manures, chicken manure gave the best performance in suppressing nematode. Based on all above, we further design organic additive 5 (chicken manure:cow manure:crab shell=10:4:1) to combine with P. lilacinum. The field experiment showed that additive 5 combined with P. lilacinum can significantly suppress gall numbers on tomato roots with the maximum control efficacy of 84.0%, higher than that treated by P. lilacinum or additive 5 alone. Further analysis of the area under disease progress curve (AUDPC) in fifty days after transplantation showed that the AUDPC of combined use of additive 5 and P. lilacinum was 957.2, significantly smaller than the areas of additive 5 (2144.4), P. lilacinum (1547.7) and the blank control (2822.4) alone. Moreover, the combination treatment of additive 5 and P. lilacinum can effectively increase the plants stem diameter and aboveground fresh weight, promote the plants blossoming and bearing fruit, significantly increase the number of flower and fruit. The yield per plant of the combined treatment increased by 7.7%, compared with the non-treatment. The root-knot nematodes in soil were reduced by 38.1% to the maximum, compared with the blank control. The CFU of P. lilacinum in the combined treatment increased by 49.8% significantly than that in treatment by P. lilacinum alone. Thus, this research indicated that the combined use of organic compost with the bio-control microbes gave better performance in suppressing root-knot disease. The results will benefit to develop effective bio-control agents.