A 79-year-old male patient began experiencing dysphagia five years ago and was diagnosed with achalasia. He underwent endoscopic balloon dilation, which initially improved his symptoms, but they progressively worsened over time. In the past week, he experienced significant obstruction when drinking water. After a multidisciplinary consultation, POEM (Peroral Endoscopic Myotomy) was recommended as the primary treatment.We innovatively utilized the injection technique to create a "fourth space" between the esophageal muscularis propria and adventitia, which facilitates easier and safer myotomy during peroral endoscopic myotomy (POEM) for patients with achalasia.