Objective To investigate the application of thrombelastogram (TEG) in assessing the intraoperative coagulation function of patients undergoing cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Methods A total of 55 patients who underwent CRS and HIPEC from January 2020 to December 2022 were selected. Their general conditions during the perioperative period were recorded. The parameters of TEG testing, including reaction time (R), kinetic time (K), coagulation angle, and maximum amplitude (MA), were recorded before surgery (T1), during CRS period (T2, i.e., immediately after the tumor was removed), before HIPEC (T3), after HIPEC (T4), and at the end of surgery (T5). Meanwhile, the trend of parameter changes was plotted, and Wilcoxon rank sum test was performed on the parameters. According to the R value, the patients were divided into two groups: a hypercoagulable group (n=29) and a non‑hypercoagulable group (n=26). Both groups were compared for the perioperative data for multivariate logistic regression. Results In the CRS stage, compared with those at T1, K increased, angle decreased, and MA decreased at T2, with statistical differences (all P<0.05), but R increased without statistical differences (P>0.05). Compared with those at T1, K increased, angle decreased, and MA decreased at T3, with statistical differences (all P<0.05), but R decreased without statistical differences (P>0.05). In the HIPEC stage, compared with those at T3, R decreased, K decreased, angle increased, and MA increased at T5, with statistical differences (all P<0.05). Throughout the operation period, compared with those at T1, R decreased and MA decreased at T5, with statistical differences (all P<0.05), but K increased and angle decreased, without statistical differences (all P>0.05). Compared with those at T1, R decreased, K increased, angle decreased, and MA decreased at T4, with statistical differences (all P<0.05). Compared with the non‑hypercoagulable group, the hypercoagulable group showed remarkably reduced infusion volume of albumin during operation (P<0.05), and there were no statistical differences in other indicators between the two groups (all P>0.05). According to multivariate logistic regression analysis, the infusion amounts of albumin, plasma, red blood cells and crystalloid during operation and blood loss were not the risk factors of hypercoagulation. Conclusions Patients receiving CRS and HIPEC show low levels of fibrinogen and weak platelet function at the cytoreductive stage and enhanced coagulation factor activity at the peritoneal thermal perfusion stage, compared with the preoperative period.