Objective: To investigate the effect of preoperative detrusor pressure at maximum urinary flow rate (PdetQmax) on postoperative outcomes after transurethral ultrasound-guided laser-induced prostatectomy (TULIP) for benign prostatic hyperplasia (BPH). Methods: A total of 124 patients with BPH who underwent TULIP were retrospectively included. According to preoperative PdetQmax, patients were divided into group A (PdetQmax ≤ 20 cmH2O, n = 36), group B (20 < PdetQmax ≤ 40 cmH2O, n = 52), and group C (PdetQmax > 40 cmH2O, n = 36). The general information, perioperative indicators, postoperative clinical efficacy at 6 months, preoperative and postoperative functional scores at 3 and 6 months, postoperative urinary function indicators at 3 months, and incidence of postoperative complications were compared among the three groups. Results: There was a statistically significant difference in PdetQmax and BCI among the three groups (P < 0.05). Compared with group A, groups B and C had shorter postoperative catheterization duration, hospital stay, and time to spontaneous voiding (P < 0.05). Six months after surgery, there was a statistically significant difference in the improvement values and rates of International Prostate Symptom Score (IPSS) among the three groups of patients (P < 0.05), and the improvement in QoL was greater in groups B and C than in group A (P < 0.05). Three months after surgery, PV decreased and Qmax increased in all three groups (P < 0.05), but PVR remained relatively high in group A patients after surgery (P < 0.05). The incidence of postoperative acute urinary retention in group A was higher than that in groups B and C (P < 0.05). Conclusion: TULIP can improve symptoms and voiding function in patients with BPH. However, patients with low PdetQmax show relatively insufficient recovery of objective urinary function and a higher risk of acute urinary retention. Preoperative PdetQmax may serve as a useful reference for outcome expectation and perioperative management.