Objective To investigate the clinical efficacy of glucocorticoid (GC) administration after percutaneous endoscopic lumbar discectomy (PELD) for L5/S1 prolapsed lumbar disc herniation (PLDH). Methods Restropective ananlysis was made of the 116 patients diagnosed with single L5/S1 PLDH and underwent PELD in our hospital from June 2015 to January 2019. Patients accepted epidural GC injection were allocated into epidural group, intravenous GC injection into intravenous group, and intravenous placebo injection into placebo group . Numerical Rating Scale (NRS) and Japanese Orthopedic Association (JOA) scores at preoperation and postoperative 1 day, 7 days, 1 month, 3 months and final follow-up were documented to assess clinical efficacy. The excellent and good rate was evaluated according to modified MacNab criterion at final follow-up. Results At preoperation,the NRS and JOA scores were not significantly different among three groups. At postoperative 1 day, the NRS score in placebo group was highest, followed by intravenous and epidural groups, while the JOA score in epidural group was highest, followed by intravenous and placebo groups. At postoperative 7 days, the NRS and JOA scores in epidural group was lower and higher, respectively, than those in intravenous and placebo groups. At postoperative 3 and final follow-up, the NRS and JOA scores were not statistically significant different among three groups. The excellent and good rates were 96.0%, 92.8% and 97.0% in three groups at final follow-up, respectively, and no significant difference among three groups was observed. Conclusions Good clinical efficacy could be achieved in L5/S1 PLDH patients treating with PELD, which could be further improved and kept for a longer time by epidural GC injection after PELD