Objective: The aim of this study was to investigate the changes and clinical values of platelet parameters in different types of severe preeclampsia (SP). Materials and Methods: The pregnant women with SP or normal conditions were selected for the study, the platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW). and plateletcrit (PCT) were tested every four weeks, starting from 12⁺¹ to 16 gestational weeks, to compare the difference in platelet parameters between SP and normal pregnant women. Results: PLT, MPV, and PDW of the early onset group exhibited statistically significant differences than the normal group from 20⁺¹ gestational weeks, and PCT of the early onset group exhibited statistically significant differences than the normal group from 28⁺¹ gestational weeks (p < 0.05); PLT, MPV, and PDW of the late onset group exhibited statistically significant differences than the normal group (p < 0.05), while PCT of the late onset group exhibited no statistically significant difference than the normal group from 12⁺¹ gestational weeks until childbirth (p > 0.05). The comparison between the early onset group and the late onset group revealed that there existed statistically significant differences in PLT, MPV, and PDW (p < 0.05), but PCT showed no statistically significant difference throughout the pregnancy period (p < 0.05). Conclusions: The changes of platelet parameters in early onset SP patients were earlier than the late onset group, and the difference was statistically significant (p < 0.05). Measuring the platelet parameters could better reveal early-stage SP, thus guiding more personalized clinical treatments to better protect maternal and child safety.