Cover Story：Using Tbx18 lineage tracer mouse model and Tbx18 conditional knockout mouse model to explore the functions of Tbx18 in the development of the structures of coronary vascular and ventricular wall. Two types of lineage tracer mouse models are established: Tbx18-Cre/Rosa26R-EYFP and Tbx18-Cre/Rosa26R-LacZ, and Tbx18:Cre/Cre gene knockout mouse model are used in the experiment. We trace the fate of Tbx18 in the formation of the vascular and myocardial structure in the cardiovascular system by immunofluorescence and X-gal staining techniques. And we compare the structure of coronary vascular and ventricular wall in Tbx18:Cre/Cre gene knockout mouse with wild-type mouse by whole-mount PECAM immunohistochemistry, HE staining, immunohistochemistry and immunofluorescence techniques. The trace of Tbx18 shows that Tbx18 contributes to the structure of the mouse coronary vessels and interventricular septum, and Tbx18 expression co-locolize with smooth muscle cells. The comparison between Tbx18:Cre/Cre gene knockout mouse and wild-type mouse shows that the knockout mouse can form normal coronary vascular system, and there is no difference between the thickness of the ventricular wall and the interventricular septum. The gene Tbx18 contributes to the heart vascular smooth muscle and interventricular septum, but it is not necessary in the formation of coronary vascular structure and the heart chamber structure.