Objective To observe the clinical curative effect of unilateral biportal endoscopy(UBE)in the treatment of extreme lateral lumbar disc herniation(ELLDH).Methods From June 2019 to June 2022,25 patients with ELLDH were treated with UBE-guided discectomy,including 16 males and 9 females.The age ranged from 26 to 62 years with a mean of(53.67±17.45)years.History ranged from 3 d to 10 years.There were 9 cases of internal foraminal type(type Ⅰ),13 cases of external foraminal type(type Ⅱ)and 3 case of mixed type(type Ⅲ).There were 8 cases of L4/5 space and 17 cases of L5/S1 space.All the patients underwent anterior and lateral lumbar X-rays,CT and MRI scans before surgery.The visual analogue scale(VAS)pain score and Oswestry disability index(ODI)assessed lower limb and lower back pain and functional recovery before surgery and at 3 d and 3 months after surgery,respectively.Macnab criteria evaluated the immediate surgical outcome.Results The UBE technique was used to treat ELLDH.The operative time was(79.79±23.97)min,the intraoperative bleeding volume was 40～80 mL,with an average of(55.80±10.74)mL.Follow-up time was(7.02±4.26)months.Preoperative VAS of lower limb was(7.04±0.92),lower back VAS was(3.49±1.52),ODI was(35.03±2.97)%.Compared with the preoperative results,the lower limb VAS was(2.17±0.61),lower back VAS was(1.48±0.43),and ODI was(18.77±3.15)%on day 3 after surgery,lower limb VAS was(1.38±0.65),lower back VAS was(1.03±0.48)and ODI was(6.05±1.80)%on the 3 months after surgery were improved(P＜0.05).The excellent and good rate was 96.0%(excellent 20,good 4,fair 1),and no obvious complications were observed during the follow-up.Conclusion UBE is effective,with little trauma,clear intraoperative visual field,good intraoperative experience,and less traumatic and safe in the treatment of ELLDH.