Objective:To study whether aspirin has inhibitory effect on microglia activation induced by Poly-IC and its mechanism.Methods:Microglia cell line BV2 were cultured in vitro to establish a Poly-IC stimulation-induced microglia cell immune activation model. The experiment groups were divided into control group (no treatment), model group (Poly-IC 10 μg/ml), high dose aspirin group (1 mmol/L aspirin), low dose aspirin group (0.1 mmol/L aspirin), high dose aspirin pretreatment group (Poly-IC 10 μg/ml + 1 mmol/L aspirin) and low dose aspirin pretreatment group (Poly-IC 10 μg/ml + 0.1 mmol/L aspirin). The phagocytosis ability of microglia cells, reactive oxygen species (ROS) and Iba1 protein expression were detected by using immunofluorescence method. The expression of the inflammatory cytokines Il-1β, Il-6, Il-10, TNF-α and cox-2 mRNA in microglia cells were detected by real-time quantitative PCR (RT-qPCR).Results:Compared with the control group, the morphology of microglia cells in model group changed significantly, and the phagocytosis ability and production of reactive oxygen species (ROS) increased. At the meantime, the expression of Iba1 protein was strongly decreased. In the model group, The mRNA expressions of IL-1β(20.55±1.92), IL-6 (63.98±7.83), TNF-α (16.84±3.19), COX-2 (6.78±0.42) were higher than IL-1β(1.01±0.14), IL-6 (0.95±0.17), TNF-α (1.22±0.38), COX-2 (0.87±0.11) in the control group. (Il-1β ( t=26.14), Il-6 ( t=10.22), TNF-α ( t=17.06) and COX-2 ( t=37.07), all P<0.01). In the aspirin pretreatment group, the phagocytic ability of microglia cells was inhibited compared with the model group, and the production of reactive oxygen species (ROS) reduced. The expression of Iba1 protein was also partly recovered. Meanwhile, the effect of the high aspirin dose pretreatment group on pro-inflammatory factors IL-1β(9.95±0.52), IL-6 (39.64±6.89), TNF-α(1.57±0.42), COX-2 (2.47±0.14)were lower than those in the model group significantly.(IL-1β: t=14.18, IL-6: t=3.69, TNF-α: t=16.68, COX-2: t=27.03, all P<0.01). Conclusion:Aspirin has an inhibitory effect on microglial activation induced by Poly-IC, which may be related with inhibiting the expression of inflammatory factors.