Objective Our study aimed to develop a simple-to-use nomogram for predicting the occurrence of HELLP and factors that may make HELLP progression within 3 days. Design The unpredictability of HELLP syndrome and the severe adverse outcomes for both mother and child make it especially important for us to seek predictive model. Setting We used electronic data from Women’s Hospital, Zhejiang University School of Medicine, between January 1,2014 and December 31,2023. Population or Sample A total of 808 patients were included in this study, including 607 patients in non-HELLP syndrome group and 201 patients in the HELLP syndrome group. methods Single and multiple-factor logistic regression analyses were applied to screen for independent factor affecting both the occurrence of HELLP syndrome and within-3-day HELLP syndrome by R software. A nomogram of HELLP syndrome and its efficacy were developed by ROC curves. Results We developed a nomogram displayed very high discrimination (C index 0.979, CI: 0.971-0.987). In the multivariate regression analysis, blood urine nitrogen and the ratio of creatinine over blood urea nitrogen were in a good significant in predicting within-3-day HELLP syndrome. The sensitivity was found to be 68% and 65%, specificity to be 74% and 68.6% respectively. Conclusions We established a great nomogram to evaluate the occurrence of HELLP syndrome. And we found blood urine nitrogen and the ratio of creatinine over blood urea nitrogen could be efficient predictors of HELLP syndrome occurring within 3 days.