In Vietnam, leaf blight disease is caused by Xanthomonas axonopodis pv. allii on green onion. Therefore, the purpose of this research was to find bio-solution with the beneficial rhizomatous fungus. The results showed that when treated at seven days before inoculation, Penicillium had the ability to reduce leaf blight severity up to 82.99% at day three after inoculation. Moreover, the value of enzyme PAL gained 25.22 μg/protein/min at 6 hours after inoculation. In addition, results also showed that Penicillium treatment at two days before inoculation reduced disease severity by 75% and 68.75% at days two and three after inoculation, respectively. Similarly, the PAL value of this treatment was 25.66 g/protein/min.