Objective Hope that through the use of high frequency ultrasound to observe before and after endoscopic pyloromyotomy for congenital hypertrophic pyloric stenosis (CHPS) the gastric mucosa layers of pyloric canal stenosis tissue change and liquid through the pyloric canal, to discuss the clinical significance and application value of high frequency ultrasound in this new type of minimally invasive surgery. Methods 65 children with CHPS were examined by ultrasonography. The changes of the thickness of the mucosa of the pyloric tube and the diameter of the inner diameter of the pyloric tube were observed before the operation and 1 days, 1 weeks, 1 months and 6 months after the operation. Results 1 days after surgery mucosa and submucosa thickness increased as compared with that before operation; 1 weeks and 1 months after surgery the pyloric tube length , diameter, thickness of pyloric muscle decreased as compared with that before operation, no change in mucosa and submucosa thickness; 6 months after surgery, the pyloric tube length, diameter, thickness of pyloric muscle, mucosa and submucosa thickness compared with surgery decreased. The number of gastric fluid passing through the pyloric canal increased significantly after operation, and the extent of pyloric canal opening increased. Conclusion Data obtained from high frequency ultrasound before and after endoscopic pyloromyotomy for the treatment of CHPS were found, pyloric muscular layer and mucosa and submucosa thickness and pyloric stenosis improved, the minimally invasive surgical method is effective, ultrasound has important significance in evaluating the curative effect of the operation.