Objective: To investigate the application effectiveness and nursing care of mid-length catheters (MCs) in the infusion of oxaliplatin in gastrointestinal tumor patients who refuse central venous catheterization. Methods: A total of 71 patients with gastrointestinal tumors who were treated in our hospital from August 2024 to June 2025 were selected. All of them refused central venous catheterization due to subjective willingness and voluntarily accepted MC insertion for oxaliplatin chemotherapy. The MC insertion status of the patients was recorded, and the incidence of catheter-related complications during chemotherapy and the quality of life before and after intervention were observed. Results: The catheterization success rate among the 71 patients was 97.18%; the average catheterization time was (18.25 ± 1.12) minutes, and the average catheter indwelling time was (12.64 ± 4.58) days; a total of 5 catheter-related complications occurred during chemotherapy, with an overall incidence rate of 7.04%, all of which were mild to moderate complications, and no severe complications occurred; the quality of life score after intervention was significantly higher than that before intervention (P < 0.05). Conclusion: The application of mid-length catheters in the infusion of oxaliplatin in gastrointestinal tumor patients who refuse central venous catheterization offers advantages such as a high catheterization success rate, long indwelling time, low complication rate, and improved quality of life for patients. Combined with targeted nursing measures, it can further ensure medication safety.