Sepsis is one of the main causes of death in ICU patients, and accurate and stable early prediction is essential for clinical intervention. Existing methods mostly rely on traditional time series models (e.g., LSTM, Transformer) or clinical scoring criteria (e.g., SOFA, qSOFA), but face two major challenges: 1) spurious correlations in the data affect the robustness of the model; 2) Lack of modeling the underlying causal relationships in the data space. We propose a Serialized Causal Disentanglement Model (SCDM) that decouples latent variables into sepsis-related factors ($u$), other disease-related factors ($v$), and irrelevant confounders ($s$ ). Based on the MIMIC-IV v2.2 dataset (3,511 positive samples and 17,538 negative samples), SCDM took patient clinical indicators, personal information, and clinical notes as input, and achieved an AUC of 0.765-0.928in the prediction task 48 to 0 hours before the onset of sepsis. The performance is significantly better than the baseline models (e.g., Transformer's 0.662-0.910, MGP-AttTCN's 0.692-0.913). Experiments show that optimizing the time window (5 hours of continuous observation) and variable selection (45 key indicators) can improve the performance of the model. The effectiveness of causal unwinding is verified by the visualization of Grad CAM and t-SNE, key clinical indicators such as platelet count, lactic acid, and respiratory rate are further identified to provide interpretable decision support for doctors. Our study provides a high-precision and interpretable causal disentanglement framework for early prediction of sepsis, which is expected to promote the development of intelligent diagnosis and treatment in the ICU.