Objective To explore and analyze the clinical application effect of thymosin α1 combined with folfox regimen in the adjuvant treatment of patients after transabdominal radical resection of rectal cancer （RC）. Methods A total of 102 patients with RC in the hospital were included from January 2020 to January 2024， and were randomly and evenly classified into two groups by adopting random number table method. The conventional group received folfox regimen after radical resection， whereas the study group was added with thymosin α1. The levels of tumor-related factors， changes of immune function indicators， treatment safety， recurrence and metastasis， and tumor-related mortality were observed in the two groups after treatment. Results Compared with before treatment， the levels of carcinoembryonic antigen （CEA）， hypoxia-inducible factor-1α （HIF-1α）， matrix metalloproteinase-9 （MMP-9） and vascular endothelial growth factor （VEGF） in the two groups were significantly decreased， and the levels in the study group were significantly lower than those in the conventional group （P < 0.05）. After Bonferroni correction， CEA and MMP-9 were statistically different between groups （P < 0.010）. The CD83⁺， CD4⁺/CD8⁺ and NK cell activity were significantly enhanced in the two groups compared to before treatment， and the above indicators were significantly higher in the study group （P < 0.05）. After Bonferroni correction， there were statistical differences in CD83⁺， CD4⁺/CD8⁺ and NK cell activity between groups （P<0.010）. In terms of treatment safety， the total incidence rate of toxic and side effects in the study group was 23.53%， which was significantly lower than 43.14% in the conventional group （P < 0.05）. Logistic regression （stepwise forward method） analysis showed that nerve invasion， vascular tumor thrombus and folfox regimen were risk factors of tumor recurrence and metastasis （P < 0.05）. Kaplan-Meier curve revealed that patients in the study group showed a trend of survival benefit. However， Log-rank test suggested that the difference between the two groups did not reach statistical significance （P > 0.05）. COX regression analysis indicated that vascular tumor thrombus was a risk factor of tumor-related death （P < 0.05）. Conclusion The adjuvant therapy with thymosin α1 combined with folfox regimen after transabdominal radical resection of RC can effectively activate the functions of dendritic cell， NK cell and T cell， increase the killing effect of tumor cell， reduce the loads of tumor-related factors， and thus help to reduce the recurrence and metastasis rate.