Objective:To observe the resection range of dog hemi-vertical larynx by semiconductor laser.Methods: Twelve dogs were randomly divided into three groups (A,B and C,n=4).Group A: the hemi-vertical larynx was cauterized forward from the anterior commissure to thyroid cartilage internal membrane,outwards including the right vocal cords.Group B: the hemi-vertical larynx was cauterized forward from anterior commissure to thyroid cartilage internal membrane and partial cartilage of anterior commissure,outwards including the right ventricular fold,vocal cord,thyroarytenoid muscle and partial lateral cricoarytenoid muscle,downwards including the lower edge of thyroid cartilage,and backwards including the partial arytenoid cartilage.Group C: the hemi-vertical larynx was cauterized forward including the anterior commissure and partial thyroid cartilage of anterior commissure,outwards including the right ventricular fold,vocal cord,thyroarytenoid muscle,lateral cricoarytenoid muscle and paraglottic space to thyroid cartilage,downwards including the partial cricothyroid membrane to the upside of cricoid cartilage,and backwards including total right arytenoid cartilage.The recovery of the laryngeal wounds,hoarseness,and complications were observed and evaluated by using digital camera and electrolaryngoscope immediately,1 week and 4 weeks after operation.The treatment outcome of the resection was evaluated.Results: The laser surgery was completed successfully in all the animals.Laryngoscope showed that the neonatal membrane covered the wound in group A and B one week later,without obvious complications.The neonatal membrane covered part of the wound in group C,accompanied by inflammatory reaction and cough when eating.Four weeks later the new membrane over the wound surface were smooth in all the three groups; adhesion appeared in the anterior commissure and new anterior commissure was formed.A new vocal cord was formed in group A; only a small gap was seen when the glottis was closed.In Group B,the new vocal cord was narrower and thinner; granulation growth was seen in local areas; and the glottis was closed incompletely.In Group C,mucosa was slightly raised over the original location of the vocal cord.Closure of the glottis was poor.Group A had no hoarseness,Group B had moderate,and Group C had severe hoarseness,but without cough when eating.Also in Group C the lamina of thyroid cartilage of the operative side was thinner than that of the contralateral side.Conclusion: When cauterizing dog partial hemi-vertical larynx using semiconductor laser,we can resect all the soft-tissue internal the thyroid cartilage,including the arytenoid and partial thyroid cartilage in the anterior commissure.The repair is satisfactory after operation,without obvious complications.