Objective  To compare the clinical outcomes between lower tibial tunnel placement combined with internal tension relieving suture and simple lower tibial tunnel placement for posterior cruciate ligament (PCL) reconstruction. Methods The clinical data of 83 patients with simple PCL injury who met the selection criteria between January 2014 and February 2022 were retrospectively analyzed. Among them, 44 patients underwent PCL reconstruction through lower tibial tunnel placement combined with internal tension relieving suture (tension relieving suture group), and 39 patients underwent PCL reconstruction through simple lower tibial tunnel placement (control group). Baseline characteristics, including gender, age, body mass index, side of injury, cause of injury, preoperative side-to-side difference (SSD) in posterior tibial translation, visual analogue scale (VAS) score, knee range of motion (ROM), Tegner score, Lysholm score, and International Knee Documentation Committee (IKDC) scores (including symptom, daily activities, and knee function scores) were compared between the two groups, showing no significant difference (P>0.05). The operation time and intraoperative blood loss were recorded and compared between the two groups. The effectiveness was evaluated by Lysholm score, IKDC scores, Tegner score, VAS score, knee ROM, SSD in posterior tibial translation before operation and at last follow-up, the patient satisfaction at last follow-up, and the postoperative graft recovery was evaluated by MRI. Results There was no significant difference in operation time and intraoperative blood loss between the two groups (P>0.05). All patients were followed up 12-60 months, and there was no significant difference between the two groups (P>0.05). Postoperative MRI showed that the graft was in good condition, and the reconstructed PCL graft had good signal, continuity, and tension. During the follow-up, there was no complication such as re-rupture or donor site discomfort in both groups. At last follow-up, the Lysholm score, IKDC scores, Tegner score, VAS score, knee ROM, and SSD in posterior tibial translation significantly improved in both groups when compared with those before operation (P<0.05). The changes of Lysholm score, Tegner score, IKDC knee symptom score, and SSD in posterior tibial translation between pre- and post-operation were significantly superior in the tension relieving suture group compared to the control group (P<0.05). However, no significant difference was found between the two groups in the changes of VAS score, knee ROM, IKDC daily activities score or knee function score between pre- and post-operation, and the satisfaction score (P>0.05). Conclusion Lower tibial tunnel placement combined with internal tension relieving suture PCL reconstruction represents a more effective surgical approach for improving postoperative laxity of PCL and knee function recovery comparing to simple lower tibial tunnel placement PCL reconstruction.