Abstract: Inhibition spectrum and antagonistic mechanism of an endophytic fungus Trichoderma harzianum LH-7, isolated from wild medicinal plant Aloe barbadensis, were investigated by in vitro culture methods against 9 kinds of plant pathogens. The results showed that nutrient competition and hyper-parasitism were the two primarily antagonist approaches that strain LH-7 adopted to inhibit the tested plant pathogens with a significant inhibition rate of 62.4%-88.4%. Moreover, the active compound from metabolites of LH-7 could cause pathogen mycelial deformities, cell wall rupture and conidial malformation, leading to the effective inhibition on pathogens growth and reproduction.