Abstract:[Background] The Pseudomonas tolaasii-caused brown blotch disease of Pleurotus ostreatus has occurred on a large scale, resulting in low yields and potential safety risks. It is of great significance to find safe and effective antibacterial agents for the development of P. ostreatus industry. [Objective] In this study, five different methods were used to obtain Allium sativum leachate samples. The effects of A. sativum leachate samples on P. tolaasii and the mycelial growth of P. ostreatus were then tested. [Methods] The inhibition zone method was used to determine the antibacterial effects of five A. sativum leachate samples on P. tolaasii. The plate diffusion method was employed to screen out the leachate sample and the appropriate concentration that can promote the growth of P. ostreatus. [Results] The five A. sativum leachate samples had strong activity against P. tolaasii. Among them, 10% A. sativum leachate prepared with apricot shell wood vinegar had the best performance, with the antibacterial effect equivalent to that of 0.33 mg/mL streptomycin. Moreover, it significantly promoted the mycelial growth of P. ostreatus, as manifested by the dense mycelia and neat edges, which was better than that of the control. [Conclusion] This research lays an experimental foundation for the prevention and treatment of brown blotch disease infecting P. ostreatus by the combination of A. sativum and apricot shell wood vinegar.