The factors were studied in detail about the interactions of several phyllosphere non-pathogenic Microorganisms and Trichoderma. The results showed that the colonizing ability of Trichoderma could be lessened on leaf surface by Aspergillus niger，The Colonizing ability of Trichoderma could be affected by the existence of Aspergillus niger in phyllosphere before Trichoderma initiated colonization which associated with the competition to exudates and space in phyllosphere between the two fungi.