Objective To design and prepare an absorbable transthoracic left atrial appendage (LAA) reverse occluder and delivery system and to evaluate the feasibility of absorbable transthoracic LAA reverse occlusion by in vitro experiment. Methods A double-disk-shaped absorbable transthoracic LAA occluder was designed using polydioxanone (PDO), poly-L-lactic acid (PLA), and polyglycolic acid (PGA). Compression properties, elastic recovery properties and ultimate sustainable effective delivery times of the tail thread riveting were tested by in vitro water bath. Six isolated dog hearts were punctured at the center of the upper 1/3 axis of left atrial appendage under direct vision,and 14F sheath with scale was used to complete the in vitro experiment of occlusion. The location and effect of the occluder were observed by anatomizing the hearts after closure. Results Absorbable LAA occluder was smoothly delivered by 14F sheath, and instantly released and restored to 96% of original size after placed for 15 min in the sheath. Tail thread riveting could tolerate (5.20±0.75) times effective delivery. Six heart specimens successfully underwent the occluding tests in vitro. We found that the occluder was well located, with the opening disk of the left atrial appendage porting into the opening a little, and the opening was in an over distraction state. There was no influence on blood flow of pulmonary vein and function of the mitral valve. Conclusion The absorbable transthoracic LAA reverse occluder is well-designed and matches the anatomy of the left atrial appendage of canine. Further animal experiment is needed to evaluate the feasibility, safety and efficacy of the absorbable transthoracic LAA reverse occluder.