Abstract: A vascularized cardiac organoid with a chamber structure and its preparation method is presented. The cardiac organoids have a unique chamber structure, which includes a myocardium wall. Within the cardiac organoids, a vascular network is developed, enclosed within the myocardium wall. This vascular network is composed of endothelial cells surrounded by smooth muscle cells, forming a network of branched tubular structures. The presence of vasculature significantly promotes the arrangement of the myocardium, enhances the organization of the cardiac cytoskeleton, and promotes the consistency and beating frequency of cardiac cells. The vasculature facilitates the growth and size increase of the cardiac organoids.