Seromas after endoscopic totally extraperitoneal (TEP) inguinal hernia repair are still common to see, which could be a limiting factor that restrains the use of endoscopic TEP approach especially for complicated and severe inguinal hernia. Retrospective researches were carried out on 478 cases of inguinal hernia who received endoscopic TEP hernia repair from March 2009 to March 2014, including 321 draining cases and 157 non-draining cases. A total incidence of seroma was observed in 8.79 % patients of 478 cases. 13 and 29 seromas occurred in draining group and non-draining group respectively (4.05 vs. 18.47 %, P < 0.05). In both general hernia group (411 cases) and giant scrotal hernia and irreducible hernia group (67 cases) 21 patients were observed formation of seroma (5.11 vs. 31.34 %, P < 0.001). Incidence of seroma in draining vs. non-draining group of general hernia was 2.87 vs. 9.85 % (P < 0.05), and that 11.90 vs. 64.00 % of giant scrotal and irreducible hernia (P < 0.001). Pain score reduced significantly in draining group one week postoperatively compared with non-draining group (P < 0.05). Incidences of hospital stay after operation, infectious complications and hernia recurrence were comparable in draining and non-draining group (P > 0.05). Efficient drainage in preperitoneal space may effectively reduce the incidences of seroma after endoscopic TEP approach and it may be of vital significance especially in giant scrotal hernias and irreducible hernias.