Objective To explore the effects of α-linolenic acid on placental damage and NLRP3 inflammasome in preeclampsia mice.Methods The experiment was divided into a control group, a model group (100 μg·Kg-1 lipopolysaccharide), an α-linolenic acid group (500 mg·Kg-1 α linolenic acid), and an experimental group. The systolic blood pressure, diastolic blood pressure, urinary albumin/creatinine, fetal weight and placenta quality of mice were measured. The pathological changes of mouse placental tissue were observed. The enzyme-linked immunosorbent (ELISA) method was used to detect tumor necrosis factor-α(TNF-α), Interleukin-6(IL-6), interleukin-8(IL-8). Western blotting were used to detect NLRP3 inflammasome, caspase-1, and interleukin-1β(IL-1β) protein expression. Results Compared with the control group, the systolic and diastolic blood pressures of the model group and the experimental group began to increase from the 12th to the 5th day of pregnancy. Compared with the model group, both systolic and diastolic blood pressures in the experimental group showed a downward trend (P<0.05). Compared with the control group, there was no significant change in blood pressure in the alpha-linolenic acid group (P>0.05). Compared with the control group, the ratio of urine protein to creatinine in the model group significantly increased, the weights of the fetus and placenta significantly decreased, the total area of the placenta and the proportion of the area of the trophoblast cell layer of the placental labyrinth significantly decreased, and the contents of TNF-α, IL-8, IL-6 in the placental tissue significantly increased. The relative expression levels of NLRP3, Caspase-1 and IL-1β proteins in placental tissue significantly increased (all P<0.05). Compared with the model group, the ratio of urine protein to creatinine in the experimental group decreased, the weight of the fetus and placenta increased, and the total area of the placenta and the proportion of the trophoblast layer of the placental labyrinth increased. Compared with the model group, the contents of TNF α, IL-6 and IL-8 in the placental tissue of the experimental group decreased significantly, and the relative expression levels of NLRP3, Caspase-1 and IL-1β proteins in the placental tissue decreased significantly (all P<0.05).Conclusion α-Linolenic acid inhibits placental inflammatory response in preeclampsia mice and improves clinical symptoms in PE mice. The mechanism may be related to the NLRP3 inflammasome