Objective To investigate the effects of triptolide (TP) on microglial M1/M2 polarization after cerebral ischemia-reperfusion (I/R) injury in rats and the underlying molecular mechanism. Methods A rat model of middle cerebral artery occlusion (MCAO) was established. TP was administered to rats at doses of 0.1 and 0.2 mg/kg, with a sham surgery group as the control group. Longa scoring was performed to grade neurological deficits in rats; HE staining was used to observe the morphology of neurons in ischemic brain tissues; neuron-specific nuclear protein (NeuN) immunofluorescence staining was used to measure the number of neurons; and Western blot analysis was used to measure the expression levels of ionised calcium-binding adaptor molecule-1 (Iba1), inducible nitric oxide synthase (iNOS), arginase 1 (Arg1), Toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), NeuN and caspase-3 in ischemic-brain tissues. The protein levels of interleukin 1β (IL-1β) and IL-10 were measured by ELISA. Immunofluorescence double labelling was performed to detect the expression of Arg1 and TLR4 in microglia. Results Compared with the model group, the neurological score of the TP treatment group was significantly reduced and the neuronal damage was significantly alleviated. IL-1β levels decreased while IL-10 levels increased. The expression levels of iNOS, TLR4, NF-κB and caspase-3 decreased, while the expression levels of Arg1 and NeuN increased. Conclusion TP treatment ameliorates cerebral I/R injury in rats, which may be attributed to the promotion of microglial M2 polarization, thereby reducing the release of inflammatory factors and inhibiting apoptosis.