Objective:To apply endoscopic ultrasound (EUS) elastography to the evaluation of EUS-guided fine needle injection (EUS-FNI) for insulinoma.Methods:Clinical data of 21 patients with insulinoma who were treated with EUS-FNI at the digestive endoscopy center of the First Affiliated Hospital of Guangxi Medical University from April 2016 to March 2021 were collected. Some patients underwent EUS real-time elastography before and after the treatment. The minimum blood glucose, synchronous insulin, synchronous C peptide, elastic imaging color pattern, elastic score, a-elasticity, elastic imaging strain rate before and after the treatment were analyzed.Results:Among the 21 cases with 24 lesions, there were 5 males and 16 females. There were totally 39 times of injection, where 8 cases underwent single injection, and 13 cases repeated injection. After the operation, patients' symptoms improved, the minimum blood glucose increased in different degree [2.59 (1.95, 3.82) mmol/L VS 1.50 (1.00, 2.00) mmol/L, Z=-4.278, P<0.001], the level of synchronous insulin [96.69 (44.80, 249.30) pmol/L VS 159.10 (100.30, 373.70) pmol/L, Z=-1.445, P=0.148] and C peptide [3.56 (2.98, 8.05) ng/mL VS 6.16 (3.74, 11.47) ng/mL, Z=-1.825, P=0.068] decreased, but no statistical difference compared with those before the operation. Sixteen cases underwent preoperative endoscopic elastography, with elastic score of 2.00 (2.00, 3.00), and 15 cases underwent postoperative elastography with elastic score of 5.00 (5.00, 5.00). Preoperative a-elasticity was recorded in 15 cases with value of 0.16 (0.08, 0.30), and postoperative a-elasticity was recorded in 12 cases with value of 0.07 (0.05, 0.18). The preoperative strain rate were recorded in 14 cases with 2.28 (1.67, 4.38), and postoperative strain rate were recorded in 12 cases with 5.16 (2.08, 8.17). Compared with those before the operation, the postoperative elastic score increased ( Z=-4.694, P<0.001), the a-elasticity decreased ( Z=-2.099, P=0.036), and the difference in strain ratio was not statistically significant ( Z=-1.492, P=0.136). Meanwhile, the lesions of insulinoma became harder, the elastic imaging mode changed from green to blue. There were no complications such as abdominal pain, fever, or pancreatitis during and after the operation. Conclusion:EUS-FNI is safe and effective for the treatment of insulinoma. Endoscopic elastography, as a new means to evaluate the efficacy of the operation, can be used to evaluate lesion ablation and guide injection therapy.